Multimodal emulsions and processes for preparing multimodal emulsions

ABSTRACT

Multimodal emulsions comprising a blend of at least one polymeric microemulsion provide for high solids and low bulk viscosity. Convenient and versitale processes for preparing multimodal emulsions are also provided. Mannich (alk)acrylamide polymeric microemulsions are among the numerous different polymeric microemulsions which may be used to prepare the multimodal emulsions.

This is a continuation of application Ser. No. 08/408,505, filed on Mar.22, 1995, now abandoned, which in turn is a continuation of Ser. No.08/157,764 filed Nov. 24, 1993, now abandoned.

BACKGROUND OF THE INVENTION

Emulsions have been desirable vehicles for the manufacture andtransportating of synthetic polymeric flocculants, particularly highmolecular weight polymers. Among other reasons for their popularity,emulsion polymers can be prepared with higher polymer solids and providesubstantial cost savings over previous solution polymers.Microemulsions, as taught in U.S. Pat. Nos. 4,956,399; 4,956,400;5,037,863; 5,132,023 and 5,037,881, provide additional advantages withrespect to polymers exhibiting undesirable characteristics even in thecontext of emulsions, for example Mannich (alk)acrylamide polymericflocculating agents, by providing for high solids level, reduceddebilitating crosslinking and superior performance. Though many polymersare commercially available in powder form, this powder form creates dustproblems and the process of dissolving the dry solids, in aqueousmedium, is a time-consuming step.

Despite the aforesaid advantages of using emulsion polymers oversolution and powder polymers, as a practical matter, emulsions andmicroemulsions are not universally used because they can exhibitstability problems, settling tendencies and high bulk viscosity whichcan make handling difficult and costly. These problems were purportedlymitigated in U.S. Pat. Nos. 4,619,967 and 4,565,836 which discloseinverse emulsions containing a single water-soluble polymer in anaqueous phase having two distinct aqueous droplet size distributions.The process in which the patentees teach to prepare these stableemulsions, however, involves an arduous series of steps of applyingdifferent shear rates to particular portions of the emulsion to producetwo different aqueous droplet size distributions.

The inventors of the instant invention have surprisingly discovered amuch simpler, more efficient process for making stable inverse emulsionshaving two or more different aqueous droplet size distributions ormodes. In addition to providing a bimodal or multimodal emulsion havinghigh solids with low bulk viscosity and, with certain polymers, superiorflocculation performance, the process of the present invention providesfor manufacture simplification and flexibility, allows for greatercontrol over the dispersed phase or aqueous droplet sizes and can beused to prepare emulsion blends containing two or more differentpolymers. This last advantage is particularly important in view of theknown benefits of combining two different water-soluble polymers forwater treatment applications.

Japanese patent nos. 20-09500 and 63-218246 disclose the mixing of aninverse emulsion containing a cationic polymer and an inverse emulsioncontaining an anionic polymer. The resulting emulsion mixtures aredescribed as providing improvements in flocculation performance andbenefits in paper making, respectively. But there is no teaching to mixtwo or more different types of emulsions, one of which is amicroemulsion, to produce the desired multimodal emulsion having lowerbulk viscosity and higher solids as achieved by the instant invention.

In U.S. Pat. No. 5,213,693 the performance and handling benefits ofsimultaneously treating waste water with a cationic coagulant polymerand a cationic flocculant polymer are described. There, a particulatemixture containing coagulant polymer beads and flocculant polymer beadsis used to facilitate dewatering of a sludge suspension. The beadsgenerally range from about 70 to 1000 microns in size and are made byreverse phase suspension polymerization followed by drying andrecovering the dry beads from the liquid. While the patentee mentionsthat the particulate composition can be a reverse phase emulsion, ormore preferably, a reverse phase "substantially dry" dispersioncontaining the two polymers, there is no mention of using amicroemulsion and no teaching to combine two or more inverse emulsionshaving polymer-containing aqueous phases which differ in their aqueousdroplet size distribution. The aqueous droplets in the patentee'semulsions or dispersions are merely disclosed as ranging in size of upto 10 microns. No improvements in the physical properties of theemulsion are even suggested. In contrast, the process of the presentinvention blends at least two emulsions having aqueous droplet sizedistributions with different average droplet sizes, one of which resultsfrom the microemulsion. Apparently, the different droplet sizes in themicroemulsion and second emulsion used in the process of this inventionare retained in the resulting emulsion. These resulting bimodal andmultimodal emulsions (collectively called "multimodal emulsions")exhibit lower viscosity. The smaller droplets from the microemulsionwhich are retained in the final multimodal emulsion are particularlybeneficial for employing water-swellable or water-soluble polymers whichtend to crosslink, such as the Mannich (alk)acrylamide polymersdisclosed in, for example, U.S. Pat. No. 4,956,399; in such instances,the debilitating effects of large-scale crosslinking is minimized by thesmaller droplets within the bimodal emulsion.

U.S. Pat. No. 4,916,182 ('182 patent) discloses the blending of awater-in-oil emulsion containing a water soluble anionic polymer with awater-in-oil emulsion containing a water soluble cationic polymer toform an emulsion mixture which is used as an adhesive composition forwall covering. After the two emulsions are blended, the resultingemulsion is subject to high shear to create the desired particular sizerange of about from 2 to 5 microns. There is no teaching to blend twoemulsions having distinctly different aqueous droplet sizedistributions, nor is it suggested that a microemulsion be used toprepare a multimodal emulsion. The emulsion mixtures produced accordingto the '182 patent do not provide the benefits of the present inventionand the benefits of the present invention are not described in the '812patent.

As described in RubberWorld, 138, 877(1958), multimodal systems havingat least two different particle size distributions were observed asproviding reduced viscosity. Latices having average particle diametersof 950 Angstroms (Å), 1710 Å and 3250 Å were concentrated alone and invarious blend ratios of small, medium and large particles. Thesewater-insoluble styrene-butadiene latices are, however, very differentfrom the emulsion polymers of the present invention, having differentapplications and posing different problems and, having an aqueouscontinuous phase, they are not inverse emulsions.

Similarly, U.S. Pat. No. 4,456,726 discloses a method for making aconcentrated, bimodal synthetic resin dispersion which lacks structuralviscosity. Such resins must be water insoluble under the conditions ofpreparation and use and the resin dispersions have an aqueous continuousphase; thus they are completely different from the polymers used in thepresent invention.

U.S. Pat. No. 5,100,951 (the '951 patent) teaches that inverse emulsionscontaining high molecular weight cationic polymers can be combined withaqueous solutions of lower molecular weight cationic polymers. Adifferent concept of producing the combination of polymers is disclosedin columns 9 and 10 of that patent, which involves emulsifying thesolution polymer by adding oil and surfactant and applying intensemechanical agitation. The emulsified liquid polymer is then blended witha commercial emulsion polymer, which also requires intense mechanicalagitation. Such intense agitation is not required in the presentinvention in order to produce a stable multimodal emulsion. The '951patent also fails to suggest the blending of two or more emulsionshaving different droplet size distributions, such as a microemulsion anda macroemulsion. Bimodal emulsions are not disclosed on the '951 patent.The patentee in the '951 patent teaches to add additional oil andsurfactants to the emulsion polymer before mixing the liquid polymerinto the emulsion to achieve a stable blend. The use of additional oiland surfactants, which greatly increases costs, is also avoided in theprocess of the present invention.

In comparison to known methods, this invention provides a convenient,flexible process for preparing a low viscosity water-in-oil emulsionwhich can comprise more than one type of polymer. For example, twopolymers having two different ionic charges may be combined to attain asystem having a desired intermediate charge. Accordingly, the inverseemulsions produced by the process of the instant invention are superiorto emulsions in the art because they not only exhibit low bulk viscosityand high solids content, but they can accommodate more than one type ofpolymer.

Another advantage of the present invention is that the properties of themultimodal emulsion blends can be easily adjusted by simply changing theparticular ratios in which the polymeric microemulsion and secondemulsion are mixed, or by changing the ratios of microemulsion polymerto the polymer in the second emulsion. This is particularly desirablefrom a commercial standpoint because it allows for versatility informing the particular bimodal or multimodal emulsion that isappropriate for treating a particular type of aqueous dispersion. Onecan, for example, tailor the ratio of the two emulsions that are blendedto meet specific requirements and then simply mix the two emulsionsaccordingly to obtain the optimal bimodal emulsion; this is much simplerthan processes used in the art.

In yet another aspect of the present invention, a stable multimodalemulsion exhibiting superior flocculation performance is prepared usinga microemulsion comprising a water-soluble polymer-based polymer havingfunctional groups which are capable of continually crosslinking. Morepreferably, the polymer in the microemulsion is a quaternary dimethylaminomethyl (alk)acrylamide which is capable of crosslinking at ambientconditions. This microemulsion is blended with a second emulsion,preferably a macroemulsion, containing a polymer which is preferablycationic and a blend stabilizing amount of aldehyde scavenger.

The preferred stable multimodal emulsion blends produced by the presentinvention exhibit flocculation performance that is just as effective, ifnot more effective, than a single microemulsion or macroemulsioncontaining a polymer of identical charge.

SUMMARY OF THE INVENTION

In the process of the present invention, a bimodal or multimodal(collectively referred to herein as "multimodal") inverse emulsioncomprising one or more polymers within its discontinuous phase,preferably aqueous, is prepared by: (a) preparing an inversemicroemulsion which comprises a water-swellable or water-solublepolymer-containing discontinuous phase that exists in the form ofdroplets; (b) preparing a second inverse emulsion comprising awater-swellable or water-soluble polymer-containing discontinuous phasein the form of droplets having a volume average diameter which isgreater than the volume average diameter of the droplets in themicroemulsion with which it is combined; and (c) admixing themicroemulsion and second emulsion. Generally, the droplets in the secondemulsion are at least about 150 Å greater than the volume averagediameter of the droplets in the microemulsion, preferably at least about300 Å greater, more preferably at least about 1000 Å greater and mostpreferably at least about 2000 Å greater than the volume averagediameter of the droplets in the microemulsion with which it is combined.Generally, the droplets in the microemulsions used in the presentinvention have a volume average droplet diameter of less than about 2500Å preferably less than about 2000 Å and most preferably less than 1000Å. Usually the discontinuous phases (droplets) in the microemulsion andsecond emulsion are aqueous, though they may consist of 100% polymer.The term "aqueous droplet" as used herein includes droplets containing100% polymer. The polymers used in the microemulsions and secondemulsions used in the process of the instant invention arewater-swellable, preferably water-soluble. The polymer in themicroemulsion may be the same as or different than the polymer used inthe second emulsion.

Also provided are various methods of flocculating suspended solids in anaqueous dispersion using the multimodal emulsions of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

It has been discovered that an inverse (water-in-oil) microemulsioncomprising a polymer-containing discontinuous phase in the form ofdroplets can be combined with a second inverse emulsion comprising apolymer-containing discontinuous phase in the form of droplets to form amultimodal inverse emulsion. The second emulsion can be a macroemulsionor a microemulsion, provided that the droplets in the second emulsionhave a volume average diameter that is greater than the volume averagediameter of the droplets in the microemulsion with which it is blended.The microemulsions, macroemulsions and second emulsions referred toherein are inverse emulsions. It is observed that the different dropletsizes of the two emulsions are retained in the resulting emulsion suchthat at least two different droplet size distributions exist in thediscontinuous aqueous phase of the final mixture. The two or moredifferent droplet size distributions result in bimodal or multimodalemulsions (i.e. emulsions having two or more modes or droplet sizedistributions) which have been found to be superior to conventionalemulsions inasmuch as they can accommodate substantially more polymersolids, can comprise more than one type of polymer and they exhibit aviscosity which is generally lower than the expected average viscositiesof the microemulsion(s) and second emulsion(s) blended to prepare themultimodal emulsion. In many cases, particularly when the viscosities ofthe microemulsion and second emulsion are somewhat similar, theviscosity of the multimodal emulsion blend will be lower than theviscosity of either the microemulsion or second emulsion used to preparethe multimodal emulsion.

Since the process of this invention can prepare emulsions which includemore than one polymer, the multimodal emulsions of this invention maycontain a wide variety of combinations of different water-swellable,preferably water-soluble polymers such as, for example, a high molecularweight polymer and a low molecular weight polymer, a cationic polymerand an anionic polymer or a highly charged cationic polymer combinedwith a lower charged cationic polymer to provide a polymeric emulsionwith an intermediate charge. Any combination of differentwater-swellable or water-soluble polymers may be used in themicroemulsions and second emulsions that are blended to produce themultimodal emulsions of this invention. The polymers in themicroemulsion and second emulsions used in the present invention maydiffer in any way, including differing in charge, or in amount ofcomonomer or they may chemically differ, such as having differentfunctional groups. Polymer combinations for use in the present inventioninclude, but are not limited to, two or more different cationicpolymers, two or more different anionic polymers, a cationic and anionicpolymer, a cationic and nonionic polymer, an anionic and nonionicpolymer, two or more different nonionic polymers and polymers that arenormally incompatible when mixed as solution polymers. Amphotericpolymers may also be included in the microemulsions and/or secondemulsions used for practicing the present invention.

In addition to being different, the polymer in the microemulsion may bethe same as the polymer in the second emulsion. It may be preferred, forexample, to employ a quaternary Mannich (alk)acrylamide (PAM) or acopolymer of acrylamide with (meth)acryloxyethyltrimethyl ammoniumchloride in both the microemulsion and second emulsion. More preferably,however, the polymer in the microemulsion differs from the polymer inthe second emulsion.

The types of polymers suitable for inclusion in the microemulsion andsecond emulsions used in the process of the present invention broadlyinclude any type of water-swellable or water-soluble polymer, as theseterms are used in the art, including any cationic, anionic, nonionic oramphoteric polymer. Water-soluble polymers are clearly preferred. Thepolymers employed in the microemulsion and second emulsions used in theprocess of this invention are formed by emulsion polymerization ofwater-soluble ethylenically unsaturated monomer or blend of monomers.

Suitable water-soluble monomers for preparing the polymericmicroemulsions and second emulsions which are blended to form a stablemultimodal emulsion include those that will readily undergo additionpolymerization. Preferred cationic monomers include dialkylaminoalkyl(meth)acrylates and dialkylaminoalkyl (meth) acrylamides, includingtheir acid addition or quaternary ammonium salts, diallyl dialkylammonium halides, vinyl benzyltrialkyl ammonium salts, polymers formedby the reaction between an epihalohydrin or dihaloalkane and an amine,and the like. Quaternized Mannich or dialkyl amino methylated(alk)acrylamide polymers such as quaternaryN-trimethylaminomethylacrylamide prepared by functionalizing(alk)acrylamide or poly(alk)acrylamide are particularly preferred.Specific examples of preferred cationic monomers include,N-dimethylaminomethyl acrylamide; acryloxyethyltrimethylammoniumchloride; diallydimethylammonium chloride; 3-acrylamido-3-methyl butyltrimethyl ammonium chloride, 2-acrylamido-2-methyl propyl trimethylammonlium chloride, 2-methacryloyloxyethyl trimethyl ammoniummethosulfate, 2-methacryloyoxyethyl trimethyl ammonium chloride,3-methacryloyl-2-hydroxy propyl trimethyl ammonium chloride,3-acrylamidopropyldimethylamino-(3-trimethyl-2-hydroxylpropyl ammoniumchloride), 2-methacryloyloxyethyl trimethyl ammonium chloride;methacryloxyethyltrimethylammonium chloride; dimethylaminoethylacrylate,dimethylaminoethylmethacrylate or mixtures of any of the foregoing.Mixtures of any of the above cationic monomers together with acrylamideor (meth)acrylamide to prepare cationic copolymers are useful and alsopreferred for the present invention. The instant invention alsocontemplates homopolymers of the above cationic monomers, as well ascopolymers of any of the above cationic monomers, or anionic or nonionicmonomers, listed below.

The preferred anionic monomers for use in preparing the microemulsionsand/or second emulsions used in the present invention generally arevinyl anionic monomers and include acrylic acid, methacrylic acid,ethacrylic acid and their alkali metal or ammonium salts, vinyl sulfonicacid, 2-acrylamido-2-alkylsulfonic acids where the alkyl group contains1 to 6 carbon atoms, such as acrylamido 2-methyl propanesulfonic acid ormixtures of any of the foregoing and their alkaline salts. The anionicmonomers may be copolymerized with (alk)acrylamide, preferablyacrylamide or methacrylamide. Acrylamide copolymers with salts of(meth)acrylic acid may also be prepared by hydrolysis of acrylamide,though attention should be directed to the use of a proper surfactantsystem capable of withstanding high pH conditions. Especially preferredanionic monomers include acrylic acid salts and 2-acrylamido-2-methylpropane sulfonic acid salts.

The preferred ethylenically unsaturated nonionic monomers for use in thepreparation of the microemulsions and/or second emulsions used in thepresent invention are selected from acrylamide; methacrylamide;dialkylaminoethyl acrylamides; N,N-dialkylacrylamides;N-alkylacrylamides; N-vinyl-acetamide; N-vinyl formamide; N-vinylpyrrolidone and mixtures thereof. Especially preferred is acrylamide andmethacrylamide.

The preferred amphoteric polymers for use in the present inventioncomprise copolymers of one or more of the foregoing anionic monomers andone or more of the cationic ethylenically unsaturated monomers listedabove or monomers which contain both anionic and cationicfunctionalities. Moreover, small amounts of hydrophobic comonomers canbe included in the polymers employed in the microemulsions or secondemulsions used in this invention such as styrene, methylmethacrylate,methylacrylates, (meth)acrylate esters containing 1-16 carbons, vinylacetate and higher esters, acrylonitrile, vinyl chloride and the like.It is understood that the present invention is not limited to thedescription of monomers, comonomers, polymers and copolymers herein.

Preferred water-swellable or water-soluble polymers for inclusion in themicroemulsions used to prepare the multimodal polymeric emulsions of thepresent invention are cationic polymers, more preferably cationicpolymers containing monomeric units selected from quaternary dialkylaminomethyl (alk)acrylamide; dialkyl aminomethyl (alk)acrylamide;quaternary dialkylaminoalkyl (meth)acrylates; dialkylaminoalkyl(meth)acrylates; quaternary dialkylaminoalkyl (meth)acrylamides;dialkylaminoalkyl (meth)acrylamides; diallyldialkylammonium halides andcopolymers of acrylamide or methacrylamide with the foregoing monomericunits. These cationic polymeric microemulsions are preferably blendedwith a second emulsion, normally a macroemulsion, containing a cationicpolymer containing monomeric units selected from quaternary dialkylaminomethyl (alk)acrylamide; dialkyl aminomethyl (alk)acrylamide;quaternary dialkylaminoalkyl (meth)acrylamides; dialkylaminoalkyl(meth)acrylamides; quaternary dialkylaminoalkyl (meth) acrylates;dialkylaminoalkyl (meth) acrylates diallyldialkylammonium halides; andcopolymers of acrylamide or methacrylamide with the foregoing monomericunits.

Generally, however, the preferred emulsion polymer combinations willvary according to the substrate to be treated and the application forwhich the multimodal emulsion is used. For example, for flocculatingsuspended solids in municipal sludge or paper sludge, it is preferred tocombine a polymeric microemulsion comprising quaternary dialkylaminomethyl (Mannich) polyacrylamide (PAM), with a cationic polymericmacroemulsion, preferably a macroemulsion comprising polymers made from(meth)acryloxyethyl trimethylammonium halide or copolymers of acrylamideand (meth)acryloxyethyl trimethylammonium halide to form a low viscositybimodal emulsion. To treat a sludge from coal refuse it would bepreferable to combine an anionic polymeric microemulsion with an anionicpolymeric macroemulsion.

The ionic polymers used in the microemulsion and second emulsion mayalso differ in charge. For instance, the polymers can have a wide rangeof charge densities, from just a few mole percent cationic or anionicfunctionality up to 100 mole percent of cationic or anionicfunctionality based on the monomer. A cationic quaternary Mannich PAMcontained within the microemulsion may, for example, be blended with asecond emulsion, preferably a macroemulsion, containing an anionic(alk)acrylamide-based polymer.

The molecular weights of the polymers used in the microemulsion andsecond emulsion are not critical to the invention and can range from afew hundred thousand to over ten million. When a high molecular weightpolymer and a low molecular weight polymer combination is desiredhowever, it is preferred to employ the high molecular weight polymer inthe microemulsion and the low molecular weight polymers in the secondemulsion, particularly when the second emulsion is a macroemulsion. Theart recognizes that for many flocculation applications for which theemulsion blends are useful, the activity of the polymers is affected bymolecular weight.

To prepare the multimodal emulsions according to the present invention,at least one polymeric microemulsion, is blended with at least onesecond emulsion with just enough agitation to admix the emulsions in areasonable time. Intense mechanical agitation or shear is not necessary.However, if intense mechanical agitation is used in blending the two ormore emulsions, that blending process does not fall outside the scope ofthe present invention provided that at least one of the emulsions usedis a microemulsion.

In combining one or more microemulsions with at least one secondemulsion the proportions in which the emulsions are combined is notcritical. Generally, at least one percent of a microemulsion should becombined with at least 1 percent of a second emulsion. Preferably, twoor more emulsions may be combined in any proportions ranging from 99 to1 parts microemulsion to second emulsion to 1 to 99 parts microemulsionto second emulsion; more preferably the ratio of microemulsion to secondemulsion ranges from 95 to 5 parts microemulsion to second emulsion to 5to 95 parts microemulsion to second emulsion. It is important that atleast one of the emulsions to be blended is a microemulsion, whichdiffers significantly from macroemulsions.

In practicing the process of the instant invention, at least twodifferent inverse emulsions must be combined to form a multimodalemulsion i.e., an emulsion having at least two different droplet sizedistributions as measured and compared using any method used in the art,e.g., by measuring number average droplet diameter or volume averagedroplet diameter. The droplet size distributions in the multimodalemulsions of the present invention need not differ by any specificquantative amount, though generally, the maxima of one or more dropletsize distributions will differ by at least about 150 Å, preferably atleast about 300 Å, more preferably at least about 1000 Å and mostpreferably at least about 2000 Å as measured by volume average dropletdiameter. To obtain a multimodal emulsion, however, one must combine twoor more emulsions having different droplet sizes. More specifically, themicroemulsion droplet size distribution, as represented by its volumeaverage droplet size, must differ from that of the second emulsion.Volume average droplet diameter will be used herein to distinguishmicroemulsions from the second emulsions with which they are blended.While there are many known methods of determining the volume averagediameter, as the term is used herein, volume average droplet diameter isa value obtained by transmission electron microscopy using the followingequation, as applied to a count of droplets which is sufficient toattain an accurate statistical representation of the droplet sizedistribution: ##EQU1## Wherein: X_(i) =the diameter value

N_(i) =the number of droplets of each diameter value

V_(a) =volume average droplet diameter

In practicing the process of the instant invention, it is important thatthe second emulsion which is combined with a microemulsion have a volumeaverage droplet diameter which is greater than the volume averagediameter of the droplets in the microemulsion. It is preferred that thedroplets in the second emulsion be at least about 150 Å, preferably atleast about 300 Å greater than, more preferably at least about 1000 Ågreater and most preferably at least about 2000 Å greater than thedroplets in the microemulsion.

A microemulsion, for purposes of this invention, is generally defined asa thermodynamically stable composition comprising two liquids or phaseswhich are insoluble in each other along with a surfactant or surfactantmixture. Polymeric inverse microemulsions which contain a continuous oilphase and a polymer-containing discontinuous phase (usually aqueous) areprepared from thermodynamically stable monomer microemulsions. Inversemicroemulsions have a narrow droplet size distribution and are usually,but not always, optically transparent. The discontinuouspolymer-containing phase of microemulsions form droplets or micelles,which are usually aqueous and usually have a volume average dropletdiameter which is less than about 2500 Å, preferably less than about2000 Å and most preferably less than about 1000 Å. Some microemulsionsmay have a volume average droplet diameter as large as about 3000 Å.

The second water-in-oil emulsion used to prepare the compositions of thepresent invention is defined as an emulsion which may be a microemulsionor a macroemulsion containing a continuous oil phase and a discontinuousphase, which is in the form of droplets or micelles that are preferablyaqueous, and surfactant.

The term macroemulsion as used herein is defined as an emulsion which isnot thermodynamically stable and which comprises two liquids or phaseswhich are insoluble in each other along with surfactant or emulsifier;the macroemulsions used in this invention comprise a discontinuouspolymer-containing phase, preferably aqueous, in the form of droplets ormicelles.

When the second emulsion is a macroemulsion, it may be formed byconventional macroemulsion emulsion polymerization methods. If it isdesirable that the second emulsion be a microemulsion, it may beprepared by microemulsion polymerization technique as described belowprovided that the technique is modified to produce a microemulsion thathas aqueous droplets having a volume average diameter which is greaterthan the volume average diameter of the droplets in the microemulsionwith which it is being blended. Again, preferably the volume averagediameter of the droplets in the second emulsion (microemulsion) shouldbe generally at least about 150 Å, preferably at least about 300 Ågreater than, more and more preferably at least about 1000 Å greater andmost preferably at least about 2000 Å greater than the volume averagediameter of the droplets in the microemulsion with which it is combined.

The microemulsions used in the process for preparing the multimodalemulsions herein comprise a continuous oil phase, which generallyincludes a water-immiscible inert organic liquid and a surfactant orsurfactant mixture, and a discontinuous phase, preferably aqueous,containing a water-swellable, preferably water-soluble polymer. Theratio of the aqueous phase to the oil phase should be as high aspossible and is such that the aqueous phase makes up from about 0.5 toabout 3:1 part oil phase. Preferably the ratio approximates 1:1. Mostpreferably, the microemulsion comprises from about 1 to about 50% weightpercent aqueous phase, based on the total weight of the microemulsion.The amount of polymer contained within the discontinuous phase of themicroemulsions should also be as high as possible but can generallyrange from a few percent up to about 100%, weight percent, based on thetotal weight of aqueous phase. The discontinuous aqueous phase may,therefore, contain 100% polymer and 0% water. The term "aqueous droplet"used for describing microemulsions herein includes droplets containingamounts of up to 100% polymer.

The polymers employed in the microemulsions used to prepare the stablecompositions described herein are formed by microemulsion polymerizationof certain water-soluble ethylenically unsaturated monomers or blend ofmonomers. Conventional microemulsion polymerization techniques asdisclosed in, for example, U.S. Pat. Nos. 5,037,881; 5,037,863;4,681,912 and 4,521,317, the disclosures of each of which areincorporated herein by reference, may be employed.

Generally, microemulsion polymerization is produced by (i) preparing amonomer containing microemulsion by mixing an aqueous solution ofmonomers with a hydrocarbon liquid containing an appropriate amount ofsurfactant or surfactant mixture to form a water-in-oil microemulsioncomprising droplets dispersed in a continuous oil phase and (ii)subjecting the monomer-containing microemulsion to polymerizationconditions. It is not necessary to apply energy, e.g., apply shear, intothe emulsion to obtain the small droplets, although a microemulsionprepared as disclosed herein, which is also is subject to shear is notbeyond the scope of this invention.

The formation of the inverse microemulsion depends on the properselection of surfactant concentration and the hydrophilic-lypophylicbalance (HLB) of the surfact or surfactant mixture. Temperature, natureof the oil phase and composition of the aqueous phase will also affectinverse microemulsion formation.

The one or more surfactants selected should provide an HLB value rangingfrom about 8 to about 12. The required HLB may vary from this, dependingon the nature of the monomers, the nature and proportion of comonomer(if any) and the nature of the oil phase. In addition to the appropriateHLB range, the surfactant concentration must be sufficient to form aninverse microemulsion. Too low surfactant concentrations will not resultin the formation of a microemulsion, while excessively highconcentrations will increase costs without imparting significantbenefit. For example, the minimum amount of sufactant for forming aninverse microemulsion containing anionic polymer will vary depending onthe HLB of the surfactant system used; such minimum surfactant amount,based on total weight, is depicted by the hachured portion within thecurve representing surfactant concentration verses HLB value in the soleFigure in U.S. Pat. No. 4,681,912, see the Figure and column 3 lines22-37 therein. Typical surfactants useful in preparing the microemulsionused for the present invention include anionic, cationic and nonionicsurfactants. Preferred surfactants include polyoxyetheylene sorbitolfatty acids, sorbitan sesquiolate, polyoxyetheylene sorbitan trioleate,sorbitan monooleate, polyoxyethylene (20) sorbitan monooleate, sodiumdioctylsulfosuccinate, oleamidopropyldimethyl amine, sodiumisostearyl-2-lactate, polyoxyethylene sorbitol monooleate or mixturesthereof and the like.

The selection of the organic phase has a substantial effect on theminimum surfactant concentration necessary to obtain the inversemicroemulsion and may consist of hydrocarbons or hydrocarbon mixtures.Isoparafinic hydrocarbons or mixtures thereof are most desirable inorder to obtain inexpensive formulations. Typically the organic phasewill comprise mineral oil, toluene, fuel oil, kerosene, odorless mineralspirits, mixtures of any of the foregoing and the like.

Polymerization of the microemulsion may be carried out in any mannerknown to those skilled in the art. Initiation may be affected with avariety of thermal and redox free radical initiators, includingperoxides, e.g. t-butyl hydroperoxide; azo compounds, e.g.azobisisobutyronitrile; inorganic compounds, such as potassium persulfate and redox couples, such as ferrous ammonium sulfate/ammoniumpersulfate. Initiator addition may be affected any time prior to theactual polymerization per se. Polymerization may also be affected byphotochemical irradiation processes, such as ultraviolet irradiation orby ionizing irradiation from a cobalt 60 source.

Typically the surfactant and oil are pre-mixed and added to an aqueoussolution which contains the monomers and optional comonomers as definedabove and any conventional additives such as, but not limited to,chelating agents such as ethylenediaminetetraacetic acid, chain transferagents, difunctional monomers such as methylene bis(acrylamide), pHadjusters, initiators and the like. Once the aqueous and oil solutionsare combined, an inverse microemulsion forms, without the need forshearing.

It has been found that a polymer which crosslinks or is capable ofcrosslinking, such as a water-soluble polymer-based polymer havingfunctional groups which are capable of continually crosslinking atambient conditions, including a dialkyl aminomethyl (Mannich)polyacrylamide PAM, are preferably employed in the microemulsion, ratherthan the second emulsion. Microemulsions are a preferred vehicle forsuch polymers because the smaller aqueous droplets in the microemulsionstend to reduce undesirable effects resulting from crosslinking of thepolymer. This maintains polymer performance while maintaining low bulkviscosity and high solids.

More specifically, in a preferred embodiment of the instant invention asecond emulsion comprising any type of water-swellable or water-solublepolymer is blended with a microemulsion comprising a water-solublepolymer-based polymer having functional groups that are capable ofcrosslinking. These so-called functionalized polymeric microemulsionsare described in U.S. Pat. Nos. 4,956,400 and 5,037,863, the disclosuresof which are incorporated herein by reference.

The water-soluble polymers which may comprise the basis for thesefunctionalized polymers are those which are capable of reacting with afunctionalizing agent to impart a functional group thereto per se orthose which contain a group capable of being transformed into a functiongroup and exhibit cross-linking during the reaction with thefunctionalizing agent, during polymerization, during the transformationor upon aging. Also included are those polymers which are prepared frommonomers containing functional groups. Examples of suitablewater-soluble polymers include those procured from such monomers as theacrylamides such as acrylamide and methacrylamide;

N-alkyl acrylamides, such as N-methylacrylamide,

N-octylacrylamide;

N,N-dialkylaminoalkyl(alk)acrylamides such as N,N-dimethylaminomethylacrylamide,

N,N-dimethylaminopropylmethacrylamide; the hydroxyalkyl(alk)acrylatessuch as hydroxyethyl acrylate, hydroxyethylmethacrylate;

N,N-dialkylaminoalkyl(alk)acrylates such as N,N-dimethylaminoethylacrylate and methacrylate, N,N-diethylaminoethyl acrylate andmethacrylate; unsaturated primary, secondary and tertiary amines such asallyl amine, diallylamine, N-alkyldially amines, mixtures thereof andthe like. Preferably, the preferred functionalized polymers are producedfrom an (alk)acrylamide; a hydroxyalkyl (alk)acrylate; aN,N-dialkylamino-alky(alk) acrylate; or an allyl amine.

These water-soluble polymers used for making functionalized polymers maybe prepared, via known polymerization procedures, by polymerization ofthe above-enumerated monomers, alone or in conjunction with up to about99.5% by weight, based on the total weight of the polymer, of additionalnon-ionic, cationic or anionic comonomers such as acryloylmorpholine;N-vinyl pyrrolidone; N-vinylformamide; the N,N-dialkylacrylamides suchas N,N-dimethylacrylamide, N,N-dipropylacrylamide; theN,N-dialkylalkacrylamide such as N,N-dimethylmethacrylamide,N,N-dipropylmethacrylamide; diallyldialkyl ammonium chlorides; the saltsand quaternaries of N,N-dialkylaminoalkyl(alk)acrylates,N,N-dialkylaminoalkyl(alk)acryamides etc; acrylic acid; methacrylicacid; fumaric acid; itaconic acid; maleic acid;2-acrylamido-2-methylpropanesulfonic acid; styrene sulfonic acid, theirsalts, and the like.

Up to about 10% by weight, same basis, of water-insoluble comonomers mayalso be included in the base polymers used to prepare the functionalizedpolymers. Such monomers include styrene; acrylonitrile; methyl acrylate;methyl methacrylate; vinyl acetate; etc.

The functional groups possessed by the polymers of the present inventionmay be imparted thereto by (1) reacting a water-soluble polymer with anagent capable of adding a functional group thereto or (2) polymerizing amonomer capable of forming a water-soluble polymer in the presence of anagent capable of adding a functional group to the resultant polymer, or(3) polymerizing a monomer already possessing a functional group andcapable of forming, alone or in conjunction with another monomer, awater-soluble polymer; or (4) polymerizing a monomer containing a groupcapable of being transformed into a functional group and capable offorming a water-soluble polymer, (1) alone or in conjunction withanother monomer, or (2) after said group has been transformed into afunctional group.

In the first instance, a water-soluble polymer is reacted with amaterial capable of adding a functional group thereto. For example, (1)acrylamide polymers may be reacted with such materials as, aldehydes,e.g., glyoxal, formaldehyde; halogens, e.g., chlorine, bromine and thelike. (2) 2-hydroxyethyl methacrylate polymers may be reacted with suchmaterials as epichlorohydrin; glyoxal; water-soluble diisocyanates; andthe like (3) N,N-dimethylaminoethyl methacrylate polymers may be reactedwith such materials as epichlorohydrin; bischloromethyl ether;1,4-dichlorobutene-2 and the like; (4)diallyl amine polymers may bereacted with epichlorohydrin, bischloromethyl either; glyoxal;a,a-dichloroxylene and the like.

With respect to the second process discussed above, the above mentionedreactants can be added to the monomers used to prepared the polymerbefore or during the polymerization to add the functional group to theresultant polymer.

In the third process, any of the above described reactions can becarried out on the monomer first and then the resultant functionalizedmonomer may be polymerized under known conditions.

In the fourth method of preparation, the monomer being polymerizedcontains, or is made to contain, a group which is capable of beingtransformed into a functional group. For example, vinyl acetate may becopolymerized with N-vinyl pyrrolidone, the acetate groups arehydrolyzed into alcohol groups which are converted into functionalgroups by reaction with glyoxal, epichlorohydrin etc. Similarly, vinylformamide may be polymerized and then hydrolyzed after which it may bereacted as above described as with the allyl amine monomers.

In addition to those reactions discussed above between, monomers,polymers, functionalizing agents etc., the following combinations offunctionalities contained on the polymers can result in polymers whichtend to crosslink and fall within the scope of the preferred systemscontemplated herein:

amines:epoxides

amines:reactive halogens

amines:aldehydes

amines:esters

amines:silanes

amines:isocynates

amines:acid halides

amines:a,b-unsaturated carbonyl compounds

methylol:amides

methylol:amines

hydroxy:isocyanates

hydroxy:esters

hydroxy:aldehydes

hydroxy:epoxides

hydroxy:reactive halogens

hydroxy:acid halides

hyroxy:silanes

aldehydes:amides

aldehydes:thiols

thiois:reactive halogens

thiols:isocynates

thiols:acid halides

Preferred functionalized polymers for inclusion in either themicroemulsions or second emulsions used in the process of the instantinvention include glyoxalated poly(alk)acrylamide, and quaternary ortertiary Mannich poly(alk)acrylamide.

The functionalized polymers made by any of the above four proceduresshould be water-swellable or, preferably, water-soluble, and if it isnot, should be reacted with an appropriate substituent to attainwater-swellability or water-solubility. The resulting functionalizedpolymers, which are preferably substituted with at least about 0.5weight percent of functional groups, are capable of undergoingcrosslinking, a phenomena which sometimes detrimentally effects theperformance of the polymer over time. When such functionalized polymersare employed in a microemulsion, however, the detrimental effects ofcrosslinking are significantly reduced, if not overcome. This benefit ismaintained in the multimodal emulsions of the present invention, if notenhanced. The multimodal emulsions resulting from combining amicroemulsion comprising a functionalized polymer and a second polymericemulsion having a certain total charge exhibit better performance as aflocculant in sludge dewatering than a single emulsion (e.g.,macroemulsion) comprising a polymer having an identical charge, as shownin Example 114.

In another preferred embodiment of the present invention, amicroemulsion comprising a dialkyl aminomethylated (Mannich)(alk)acrylamideor quatemized derivative thereof is prepared for blendingwith a second emulsion comprising any water-swellable or water-solublepolymer. The Mannich (alk)acrylamide is preferably an acrylamide polymersubstituted with at least about 1 mole percent of tertiary aminomethylgroups and more preferably a quaternary derivative. In the secondemulsion, which is preferably a macroemulsion, it is preferable to use acationic polymer and more preferably an (alk)acrylamide-based cationicpolymer including, but not limited to, cationic polymers containingmonomeric units selected from quaternary dialkyl aminomethyl(alk)acrylamide; dialkyl aminomethyl (alk)acrylamide quaternarydialkylaminoalkyl (meth)acrylamides; dialkyl aminoalkyl(meth)acrylamides and copolymers thereof with acrylamide or(meth)acrylamide with a monomer selected from quaternarydialkylaminoalkyl (meth)acrylates dialkylaminoalkyl (meth)acrylates anddiallyldialkylammonium halides. Among these, copolymers of acrylamidewith quaternary dialkylaminoalkyl (meth)acrylates are particularlypreferred and copolymers of acrylamide andmethacryloyloxyethyltrimethylammonium salt (including halides andsulfites) are most preferred, particularly those having a 1 to 60 molepercent cationic functionality, based on the monomer, more preferably1-20 mole percent. Optionally, a difunctional monomer such as methylenebisacrylamide or the like may be incorporated into the monomer solutionprior to polymerization. Any cationic polymer containing about 1-60 molepercent, most preferably 1-20 mole percent cationic functionality, basedon monomer, may be employed in the second emulsion. Microemulsionscontaining a cationic polymer preferably a quaternized or tertiartyMannich PAM, more preferably those polymers containing from about 20 toabout 100 mole percent cationic functionality, based on the monomer,more preferably from about 60 to about 90 mole percent cationicfunctionality, may be combined with the second emulsions comprising anywater-swellable or water-soluble polymer including the preferredcationic (alk)acrylamide-based polymers described above. While it ismost preferred to include a quaternary Mannich (alk)acrylamide polymerin the microemulsion, the unquaternized Mannich acrylamide polymer isalso contemplated within the scope of this preferred embodiment.

In yet a most preferred embodiment of the instant invention, amultimodal composition comprising a blend of two emulsions, one of whichis a microemulsion containing in its discontinuous phase a quaternizedMannich PAM and the second, which is preferably a macroemulsion,containing in its discontinuous phase a copolymer of acrylamide and aquaternary dialkylaminoalkyl (alk)acrylate such as(meth)acryloyloxyethyltrimethyl ammonium salt which includes halides andsulfites. The quaternized Mannich PAM should have a cationic chargewhich differs from the cationic charge on theacrylamide/(meth)acryloyloxyethyltrimethyl ammonium salt. Generally,such preferred blends comprise a quaternary Mannich PAM containing fromabout 20 to about 100 mole percent cationic functionality, based on themonomer, more preferably from about 60 to about 90 mole percent cationicfunctionality, based on monomer blended with a second emulsion,preferably a macroemulsion, comprisingacrylamide/(meth)acryloyloxyethyltrimethyl salt copolymer containingfrom about 1 to about 60 mole percent cationic functionality based onmonomer, preferably from about 1 to about 20 mole percent cationicfunctionality, based on the monomer. For example, combinations of aquaternary Mannich PAM microemulsion having a 75% cationic charge withan (alk)acrylamide/(meth)acryloyloxyethyltrimethyl halide copolymermacroemulsion having a 10% cationic charge may be blended at differentratios and with aldehyde scavenger to provide stable emulsion blendshaving a variety of intermediate charges such as polymer combinationswith 55%, 35% and 20% total cationic functionality, based on themonomer. Great cost advantages are attained by preparing this bimodalemulsion in this manner, as opposed to synthesizing a single polymericemulsion having a 55%, 35% or 20% cationic charge. And, the resultingpolymeric emulsion blends may exhibit flocculation performance that isjust as effective, if not more effective, than a single microemulsion,macroemulsion or a solution containing a similar polymer of identicalcationic charge.

In yet another embodiment of the present invention, microemulsionMannich PAMs and quaternized derivatives thereof are combined with asecond emulsion, preferably a macroemulsion, containing anywater-swellable, preferably water-soluble, anionic polymer, mostpreferably an (alk)acrylamide-based anionic polymer, most preferably ananionic polymer selected from and copolymers of (alk)acrylamide with oneor more anionic monomers selected from acrylic acid, methacrylic acid,acrylates and their alkali metal or ammonium salts; vinyl sulfonic acid;acrylamido-2-methyl propanesulfonic acid and their salts; andhomopolymers of (meth)acrylic acid,acrylic acid, vinyl sulfonic acid;acrylamido-2-methyl propanesulfonic acid; acrylamido-alkyl sulfonic acidor their alkali metal salts. Preferred anionic polymers employed in themicroemulsions used in the present invention contain from about 20 toabout 100 mole percent anionic functionality, based on the monomer, morepreferably from about 60 to about 90 mole percent anionic functionality,based on monomer. Preferred anionic polymers employed in the secondemulsions used in the present invention contain from about 1 to about 60mole percent anionic functionality based on monomer, preferably fromabout 1 to about 20 mole percent anionic functionality, based on themonomer.

Multimodal compositions comprising blends of polymeric microemulsions,preferably quaternary Mannich PAM microemulsions, with second emulsions,preferably macroemulsions, containing any nonionic water-soluble polymersuch as acrylamide or methacrylamide are also contemplated within thescope of this invention.

In a broad sense, it is also within the scope of this invention tocombine any of the following water soluble polymeric emulsions: acationic polymeric microemulsion, preferably a quaternary Mannich PAM,with non-ionic or anionic polymeric second emulsions and to combinenonionic or anionic polymeric microemulsions with cationic, anionic ornonionic polymeric, preferably (alk)acrylamide-based polymeric, secondemulsions.

The Mannich acrylamide polymer-containing microemulsion is prepared byadmixing an aqueous solution comprising acrylamide monomer with a liquidhydrocarbon, such as a low odor paraffin oil, which contains a suitablesurfactant such as a mixture of polyethylene sorbitol fatty ester andsorbitan sesquioleate. Optionally, additional vinyl comonomers such asthose described above, may be included in the above mixture and apolymerization catalyst may be additionally included. The resultingadmixture forms a water-in-oil microemulsion which is subject topolymerization conditions, reacted with an effective amount offormaldehyde and a secondary amine, or a complex formed by aformaldehyde and secondary amine, to form an amino methylatedpolyacrylamide or Mannich PAM.

Formaldehyde compounds useful in preparing Mannich acrylamide polymersare selected from formaldehyde, paraformaldehyde, trioxane or aqueousformalin, and the like. Useful secondary amines are generally selectedfrom those containing 2 to 8 carbon atoms which are aliphatic, cyclic,straight chained, branched or substituted. Preferred secondary aminesinclude dimethylamine, methylethylamine, diethylamine, amylmethylamine,dibutylamine, dibenzylamine, piperidine, morpholine, ethanolmethylamine,diethanolamine or mixtures thereof.

A preferred method of amino methylation involves a process wherein theformaldehyde comprises formalin and the secondary amine comprisesdimethylamine. It is also preferred to employ a formaldehyde-secondaryamine complex such as N,N-dimethylaminomethyl alcohol. The ratio offormaldehyde to amine is not critical and can range from about 10:1 to1:10 by mole, respectively. It is generally preferred, however, to use amolar ratio as close to 1:1 as practical. A sufficient quantity of theamine and formaldehyde, or complex thereof, is required to aminomethylate and impart tertiary amino methyl groups to the (alk)acrylamidepolymer, preferably to impart at least 1 mole percent of tertiaryaminomethyl groups. The Mannich PAM may be quaternized by methods knownin the art, such as by reacting the Mannich polymers with quatemizingagents such as methyl chloride, dimethyl sulfate, benzyl chloride andthe like under known conditions.

The amino methylation or Mannich reaction is preferably performed aftermicroemulsion monomer polymerization by adding formaldehyde andsecondary amine to the polymer to form the tertiary aminomethylsubstitutent on the polymer backbone. It is also possible, to performthe Mannich reaction at various stages in relation to inversemicroemulsion monomer polymerization. For example, one may react the(alk)acrylamide monomer with the formaldehyde and secondary amine priorto the inverse microemulsion formation and before polymerization of themonomers. Also contemplated, is adding the formaldehyde and secondaryamine to the aqueous solution prior to polymerizing and thensimultaneously polymerizing the (alk)acrylamide monomer and carrying outthe Mannich reaction. However, these alternative procedures are lesspreferred than adding the formaldehyde and secondary amine after inversemicroemulsion monomer polymerization is complete. The preparation ofMannich acrylamide polymers and quaternized derivatives thereof isfurther described in U.S. Pat. No. 5,037,881 which is incorporatedherein by reference.

Quaternized Mannich (alk)acrylamide polymers are preferably heat treatedin their microemulsion form, before being blended with the secondemulsion. Heat treatment is conducted according to the procedure in U.S.application Ser. No. 08/018,858, filed on Feb. 12, 1993, which isincorporated herein by reference. Generally, heat treatment is performedby (a) adding to the untreated quaternized Mannich PAM microemulsion,with agitation, an aqueous solution containing an acid such that the pHrange of the resulting quatemized Mannich PAM microemulsion is fromabout 3.6 to about 4.8; preferably about 3.8 to about 4.6, and adding aformaldehyde scavenger, (b) adjusting the polymer content of the aqueousphase to about 10 to about 45 wt. percent, preferably about 20-40, wt.percent, and (c) heating the quaternized Mannich PAM polymermicroemulsion obtained in step (b) to a temperature of from about 40° toabout 80° C. for from about 3 to about 20 hours.

Any water-soluble acid may be used in this heat treating procedure. Theacid is preferably employed as an aqueous solution and preferablycomprises (i) an organic carboxylic acid, an inorganic acid or acombination thereof in an amount sufficient to provide a pH of fromabout 3.6 to about 4.8 in the resulting emulsion; (ii) from about 0.01to about 30 mole percent of a formaldehyde scavenger based on the totalmoles of quatemized Mannich PAM microemulsion; and (iii) water, ifnecessary, in an amount such that when added to the microemulsion theresulting aqueous phase contains from about 10 to about 45 weightpercent of quartemized amino methylated PAM microemulsion.

The acid, preferably an organic carboxylic acid, inorganic acid and/orcombination thereof, is used in sufficient quantity such that theresulting pH of the microemulsion is from about 3.6 to 4.8, preferably3.8-4.6. The quantity of each individual acid or combination of acidsemployed in the stabilized solution is determined by acidity (pKa) ofeach individual acidic component. The total amount of acid used in thepractice of the present invention may vary from about 1 to about 40 molepercent based on the total number of moles of polymer present in themicroemulsion. The only limitation on the acid used is that it be inertwith respect to the ingredients which are present in the microemulsionsystem, i.e. emulsifier, polymer, oil and other generally addedingredients.

Acids which may be employed for use herein include, but are not limitedto, mono and multifunctional carboxylic acids such as acetic, maleic,fumaric, formic, acrylic, succinic, lactic, citric and the like;inorganic acids such as sulfurous, phosphoric, phosphorous and sulfuricacids as well as salts of these acids such as the alkali salts ofsulfurous acid, aluminum sulfate, aluminum chloride, sodium sulfate andthe like. Any combination of the above-mentioned acids may be employedas long as the quaternized Mannich PAM microemulsion has, after theaddition of the stabilizer solution, a pH within the range set forthabove.

The formaldehyde scavengers useful for stabilizing the microemulsion arethose water-soluble compounds which have the capability to react withformaldehyde. The source of formaldehyde in the quaternized Mannich(alk)acrylamide polymer microemulsion of the present invention results,in theory, from unreacted formaldehyde or from labile formaldehydecomponents that release formaldehyde. The quantity of formaldehydescavenger used in the present invention ranges from about 0.01 to about30 mole percent, preferably ranging from about 0.6 to about 15 molepercent, based on the moles of polymer in the microemulsion.

Typical formaldehyde scavengers are those known in the art, and include,but are not limited to, urea, substituted ureas such as ethylene urea,guanidine salts, dicyandiamide, sulfurous acid and any of its alkalimetal salts such as sodium bisulfite, sodium metabisulfite and the like,as well as phosphorous acid and mixtures of any of the foregoing.

The quantity of water preferably used in the stabilizer solutions isselected such that the resulting aqueous phase of the microemulsioncontains from about 10 to about 45 weight percent polymer, based on theweight of the total aqueous phase, preferably from about 15-40 weightpercent, same basis.

The formaldehyde scavenger and the acid, preferably in the form of anaqueous solution, thereof, as described hereinabove, are then added tothe microemulsion with mixing. The resulting microemulsion is thenheated to a temperature ranging from about 40° to about 80° C. for atime of from about 3 to about 20 hours. The heating step can be carriedout immediately after addition of the acid, scavenger and/or water,however, it is also possible to delay the heating up to the desired timeof use of the microemulsion as a flocculant.

The stabilized quaternized Mannich PAM microemulsion obtained after theheating step will successfully invert when added to water independent ofthe temperature or pH of the water used. The aforesaid heat treatingstep is preferred, but not essential, for microemulsions comprisingquaternary Mannich (alk)acrylamide polymers which are used for preparingemulsion blends. When heat treating is not performed, the inversion ofthe emulsion blends are more dependent on pH and temperature. When themicroemulsion used for preparing the emulsion blend does not containformaldehyde, as with other polymers, then the heat treating stepdescribed above need not be performed.

Another preferred embodiment is directed to a multimodal emulsioncomprising a blend of at least two emulsions wherein at least oneemulsion is a microemulsion containing a water-swellable orwater-soluble glyoxalated (alk)acrylamide.

Microemulsions containing glyoxalated (alk)acrylamide polymer are knownin the art and disclosed, along with their methods of preparation, inU.S. Pat. No. 4,954,538 the disclosure of which is incorporated hereinby reference.

It is also preferable to stabilize the multimodal emulsion blend byadding, to either the blend of microemulsion and second emulsion, to themicroemulsion or to the second emulsion before blending, a blendstabilizing amount of aldehyde scavenger. This treatment is moreparticularly used according to the disclosure in U.S. patent applicationSer. No. 08/157,795, filed Nov. 24, 1993 which is concurrently filedherewith and incorporated herein by reference. Generally, the additionof a blend stabilizing amount of aldehyde scavenger is employed when themultimodal emulsion blend contains: 1) a polymer,typically an(alk)acrylamide-based polymer, capable of deteriorating as a result ofreacting with any aldehyde compounds, and 2) a polymer, morespecifically called a functionalized polymer, which contains, generatesor is capable of generating an aldehyde such as formaldehyde,acetaldehyde or glyoxal. More preferably, an aldehyde scavenger is usedwhen a quaternary Mannich Pam, Mannich PAM or glyoxalated PAMmicroemulsion is blended with a second emulsion comprising any(alk)acrylamide-based polymer, preferably a polymer containing monomericunits selected from dialkyl aminomethyl (alk)acrylamide; quaternarydialkyl aminomethyl (alk)acrylamide; quaternary dialkylaminoalkyl(meth)acrylamides, dialkylaminoalkyl (meth)acrylamides;acrylamido-2-alkyl sulfonic acid or copolymers of acrylamide ormethacrylamide with any of the foregoing monomers or a monomer selectedfrom quaternary dialkylaminoalkyl (meth)acrylates anddiallyldialkylammonium halides.

The term "aldehyde scavenger", as used herein, means and includes thosecompounds, preferably water-soluble compounds, which have the capabilityof reacting with any aldehyde, such as formaldehyde, acetaldehyde,glyoxal, and the like, though preferably formaldehyde. Such aldehydecompounds are present in or generated from the microemulsion which isblended with the second emulsion to produce the stabilized compositionand they result, in theory, from unreacted aldehyde or from componentsthat release aldehyde. Suitable aldehyde scavengers include those knownin the art, and include, but are not limited to, urea, substitutedureas, such as ethylene urea, guanidine salts, dicyanamide, dimedone(5,5-dimethyl-1,3-cyclohexanedione), sulfurous acid and any of itsalkali metal salts such as sodium bisulfite, sodium metabisulfite andthe like, as well as phosphorous acid, and mixtures of any of theforegoing. Urea, substituted ureas and dimedone and mixtures thereof arepreferred.

"Blend stabilizing amount" generally refers to the amount of aldehydescavenger necessary for stabilizing the multimodal emulsion blend, i.e.maintaining performance of the polymer activity in the emulsion blend.Preferably, "blend stabilizing amount" means the amount of aldehydescavenger necessary for reducing polymer degradation (e.g. throughcross-linking or otherwise), primarily the (alk)acrylamide-basedpolymer. This amount is provided by adding from about 0.1 to about 10weight percent aldehyde scavenger, based on the total weight of thecomposition, to the emulsion blend. The three methods of adding thealdehyde scavenger to the blend are described below. The quantity ofaldehyde scavenger used in the present invention may generally be as lowas about 0.1 weight percent, based on the weight of the stabilizedcomposition, preferably at least about 0.7 weight percent, based on theweight of the stabilized composition. Generally amounts ranging up toabout 10.0 weight percent, preferably up to 5.0 weight percent, based onthe weight of the stabilized composition, may be used. While higheramounts of aldehyde scavenger are also effective, such amounts areusually less desirable since the benefits are usually offset by costconsiderations. Blend stabilizing amounts of aldehyde scavenger used inthe present invention preferably range from about 0.7 to about 5.0weight percent, based on the total weight of the stabilized composition.However, these amounts may vary as discussed below, depending upon themicroemulsion used. The blend stabilizing amount of aldehyde scavengermay be added neat or it may be added as an aqueous solution, usuallyabout a 40 to 60 weight percent solution.

The stabilized compositions of the present invention, which comprise ablend of at least two emulsions, may be prepared by three differentmethods. They are prepared by:

(a) preparing a microemulsion containing a water-swellable orwater-soluble functionalized polymer;

(b) preparing a second emulsion containing a water-swellable orwater-soluble (alk)acrylamide-based polymer;

(c) admixing the microemulsion and the second emulsion to form a blendof emulsions; and

(d) adding a blend stabilizing amount of aldehyde scavenger to theemulsion blend.

Alternatively, instead of adding the aldehyde scavenger to the emulsionblend, the stabilized multimodal emulsions of the present inventions maybe prepared by:

(a) preparing a microemulsion comprising a water-swellable orwater-soluble functionalized polymer;

(b) preparing a second emulsion comprising a water-swellable orwater-soluble (alk)acrylamide-based polymer and a blend stabilizingamount of aldehyde scavenger; and

(c) admixing the microemulsion and the second emulsion.

A third method of preparing the stable multimodal emulsions of thepresent invention is by:

(a) preparing a microemulsion comprising a water-swellable orwater-soluble functionalized polymer;

(b) preparing a second emulsion comprising a water-swellable orwater-soluble (alk)acrylamide-based polymer;

(c) adding a blend stabilizing amount of aldehyde scavenger compound tothe microemulsion resulting from step (a).

(d) admixing the microemulsion resulting from step (c) and secondemulsion to form a blend of emulsions.

It is preferred to add the aldehyde scavenger to the second emulsion,particularly if it is a macroemulsion, and then admix the microemulsionthereto. While a blend stabilizing amount of aldehyde scavenger may beadded to the second emulsion at any stage, it is preferred to add it tothe aqueous monomer phase of the second emulsion before polymerizationfor manufacturing and handling reasons and to maximize the solidscontent. In contrast, while a blend stabilizing amount of aldehydescavenger may be added to the functionalized-polymer containingmicroemulsion prior to blending, the aldehyde scavenger should not beadded to the aqueous monomer phase of that microemulsion, but must beadded to the microemulsion after it has been prepared andfunctionalized. This is to assure that sufficient aldehyde scavengerenters the droplets of the second inverse emulsion for stabilization.

It is also preferred to heat treat the microemulsion when it contains aquaternary Mannich PAM, Mannich PAM or glyoxalated PAM before mixingwith the second emulsion and to add a blend stabilizing amount ofaldehyde scavenger to the emulsion blend, preferably directly to thesecond emulsion prior to blending. The method of heat treating,described below, involves the addition of an acid to adjust the pH toabout 3.6 to 4.8 and a formaldehyde scavenger and heating themicroemulsion to a temperature within a range from about 40° to 80° C.for about 3 to 20 hours. The amount of formaldehyde scavenger that isadded to the microemulsion in this heat treating step may alter theblend stabilizing amount of aldehyde scavenger that is added to thesecond emulsion or the emulsion blend.

While heating and adjusting the pH of the microemulsion is critical toheat treating the microemulsion, the present method of preparing thestabilized blend of emulsions does not require heating or pHadjustments. Generally and preferably, the microemulsion, which isoptionally heat treated, is simply mixed with the second emulsioncontaining a blend stabilizing amount of aldehyde scavenger at ambienttemperature and with modest mixing. Less preferably, the aldehydescavenger may be added to the blend of the microemulsion and secondemulsion or to the microemulsion prior to blending at ambienttemperatures and with modest mixing conditions. The above procedureapplies regardless of whether the second emulsion is a macroemulsion ora microemulsion.

The art recognizes that certain aldehyde scavengers may not be effectiveat certain pH's, i.e., that they do not react with formaldehyde, andtherefore, even though the stabilization method of the instant inventiondoes not necessitate any specific pH range, it is important that theparticular aldehyde scavenger used to prepare the stable emulsion blendbe effective at the pH of the emulsion blend. Thus, pH adjustments maybe made, based on the known chemistry of the aldehyde scavenger used.For example, urea is known to be less reactive with formaldehyde atalkalinity levels above a pH of 7, so it would be preferred to adjustthe pH of the emulsion blend to a pH ranging from 6 to 2. Similarly, pHadjustments may be necessitated by the known chemistry of the particular(alk)acrylamide-based polymer used in the microemulsion or secondemulsion. Any such pH adjustments may be made based on knowledge in theart and with routine experimentation, if necessary.

When the second emulsion is a microemulsion it can be prepared accordingto conventional microemulsion polymerization procedures, such asdisclosed above, except that the formulation should be adjusted toobtain a microemulsion comprising polymer-containing aqueous dropletshaving a volume average droplet diameter that is greater than the volumeaverage diameter of the aqueous droplets in the microemulsion with whichit is combined. For example, if one desired to combine a microemulsioncomprising droplets having a volume average droplet diameter of 1000 Åwith a second emulsion, then the second emulsion may be a microemulsiongenerally having an average droplet diameter of at least about 1150 Å,preferably at least about 1300 Å, more preferably at least about 2000 Åand most preferably at least about 3000 Å. Using common knowledge ofthose skilled in the art, along with simple experimentation, one canmodify the microemulsion polymerization to obtain slightly largeraqueous droplets.

Alternatively, the second emulsion may be a conventional water-in-oilmacroemulsion, in which case, it is prepared by conventionalmacroemulsion polymerization methods known in the art, such as, forexample, that disclosed in U.S. Pat. No. 3,284,393 to Vanderhoff et al,the disclosure of which is incorporated herein by reference. Any knownpolymerizable water-soluble ethylenic unsaturated monomer, includingthose specifically described above, which produce water-swellable orwater-soluble polymers that are insoluble in the continuous oil phase,and can be polymerized, may be used to prepare the inversemacroemulsions used in the process of the present invention. Thewater-soluble monomers and monomer mixtures are polymerized to low orhigh molecular weight polymers or copolymers using a water-in-oilemulsion polymerization procedure in which the water-soluble monomersare emulsified in an oil phase by means of a water-in-oil emulsifier andsubject to polymerization conditions to form the inverse macroemulsionwhich is used in the process of the instant invention. The monomercontent in the aqueous solution can vary anywhere between about 5 and100% by weight monomer, though this may vary depending on the monomerand temperature of polymerization. Thus, the discontinuous phase ordroplets are usually aqueous but may consist of 100% polymer, and 0%water and are prepared using methods known in the art. The term "aqueousdroplets" as used for describing macroemulsions herein includes dropletscontaining amounts of 100% polymer.

The ratio of aqueous phase, which is defined as the monomers or polymerand water, to oil phase widely varies between about 0.1:1 to about 4:1,preferably, between about 1:1 to 4:1. The oil phase includes thehydrocarbon liquid and the surfactant dissolved or dispersed therein.

An emulsifying agent of the water-in-oil type is used in amounts rangingfrom about 1 to about 6% by weight of the aqueous phase, in order toemulsify the monomer-containing aqueous phase into the oil phase. A widevariety of conventional water-in-oil emulsifying agents which aretypically used to prepare macroemulsions may be used, such hexadecylsodium phthalate, sorbitan monoleate, sorbitan monostearate, cetyl orstearyl sodium phthalate, metal soaps, and the like. Upon performingrelatively simple tests one skilled in the art would be able todetermine whether a specific water-in-oil emulsifying agent oremulsifier mixture would be adequate for a particular system.

The oil phase can be any inert hydrophobic liquid such as, for example,hydrocarbons, perchloroethylene, aryl hydrocarbons, such as toluene andxylene. Preferably paraffin solvents are used.

Polymerization of the macroemulsion may be carried out pursuant to thosemethods known in the art, including high energy irradiation such asgamma irradiation CO⁶⁰, ultraviolet irradiation or the like. Freeradical initiators may also be used, such as potassium persulfate, aswell as azo compounds, peroxides and redox pairs or the like. Certainpolymerization methods may preferably be carried out at elevatedtemperatures.

Preferably, the emulsifying agent is dissolved in the oil phase and themonomer-containing aqueous phase is added to the oil phase withagitation until the aqueous phase is emulsified in the oil phase.Additional conventional additives such as chelating agents, smallamounts of chain transfer agents and difunctional monomers such asmethylene (bis)acrylamide, may also be dissolved in the aqueous phase ormixed into the inverse emulsion. Polymerization agents, such as freeradical initiators, may be dissolved in the oil or aqueous phase or theemulsion. Polymerization is conducted preferably with agitation, untilconversion is substantially complete. The resulting polymericmacroemulsion may be subsequently stabilized or treated according to anymethods known in the art.

While the preferred embodiment of this invention contemplates blendingone polymeric microemulsion with one second emulsion, which ispreferably a macroemulsion, the instant claimed invention may be appliedto the blending of more than two emulsions, such as blending two or moremicroemulsions with one macroemulsion or blending one microemulsion withtwo or more macroemulsions. In cases where two or more microemulsionsare combined with a second emulsion, the volume average aqueous dropletdiameter in the second emulsion must be greater than, generally at leastabout 150 Å greater, preferably at least about 300 Å greater, morepreferably at least about 1000 Å greater and most preferably at leastabout 2000 Å greater than the smallest volume average aqueous dropletdiameter among the microemulsions. In cases where two or more secondemulsions are combined with one microemulsion, the second emulsionhaving the largest volume average droplet diameter must be greater than,generally at least about 150 Å greater, preferably at least about 300 Ågreater, more preferably at least about 1000 Å greater and mostpreferably at least about 2000 Å greater than the volume average dropletdiameter of the droplets in the microemulsion. A variety of polymercombinations may be incorporated in the foregoing.

The mulltimodal emulsions produced by the present invention are usefulin facilitating a wide variety of solid-liquid separation operationssuch as flocculation for waste water treatment or for paper manufactureprocesses, the clarification of deinking process waters and the like.The polymeric multimodal emulsions may be used in the dewatering ofbiologically treated suspensions, such as sewage and other municipal orindustrial sludges, the drainage of cellulosic suspensions such as thosefound in paper production, in the treatment of paper waste, andsettlement of various suspensions, i.e., refinery waste, food waste,etc. The stable emulsions of the present invention may also be used asretention aids, wet strength or dry strength agents in the manufactureof paper, for protein recovery and as mining waste treating and settlingaids.

With respect to flocculation applications, the multimodal emulsions maybe employed in its emulsion form or in the form of a dilute aqueouspolymer-containing solutions prepared by inverting the emulsion intowater, optionally in the presence of a breaker surfactant. When breakersurfactant is added, it should be in an amount sufficient to enable theinverted polymer or polymer combination to reach its maximum solutionviscosity. Optionally, the breaker surfactant may be added to themicroemulsion or the second emulsion or both before mixing the two.

In addition to inverting the multimodal emulsions of the presentinvention, the polymers in the multimodal emulsion blends may berecovered from the emulsion by conventional means, such as by strippingor by adding the emulsion blend to a solvent which precipitates thepolymer, e.g., isopropanol or acetone, filtering off the resultantsolids, drying and redispersing in water to form a dilute aqueoussolution containing polymer. Dilute aqueous solutions include solutionscontaining water-swellable as well as water-soluble polymers. Theemulsion blends of the present invention may also be stripped toincrease the percentage of polymer solids.

Since the stabilized compositions produced herein can contain twodifferent polymers, they can be used to provide both a cationic and ananionic polymer or a high molecular weight polymer and a low molecularweight polymer substantially simultaneously for facilitating theseparation of suspended solids from aqueous dispersions containingsuspended solids. The advantage of this is that a single handlingapparatus and single dosage point may be employed to use two differentpolymers.

An alternative method of practicing the present invention is to blend,substantially simultaneously into the aqueous medium to be treated,flocculating amounts of the one or more microemulsions with thesecondary emulsion(s). For example, if one desired to use a multimodalemulsion for flocculating municipal sludge, one could add themicroemulsion(s) and second emulsion(s) substantially simultaneouslyinto the sludge dispersion to be treated and mix the two or moreemulsions within the dispersion. This may be less preferred.

Flocculating amount is the amount of emulsion or dilute aqueous solutionfor sufficiently flocculating suspended solids in an aqueous dispersion.That amount will depend upon the particular application and the severityof the problem addressed. For the flocculation of paper sludge ormunicipal sludge, for example, it is preferable to use an amount ofemulsion or dilute aqueous solution capable of providing anywhere fromabout 0.02 to about 200 pounds total polymer per ton of dry sludge, morepreferably from about 1 to about 100 pounds total polymer per ton of drysludge. The appropriate dosage for each application may be easilyascertained by simple experimentation or from knowledge in the art.

It is believed that one skilled in the art can use the precedingdescription to utilize the present invention to its fullest extent.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples are set forth for illustration purposes only andare not to be construed as limitations on the present invention, as setforth in the appended claims.

Standard Viscosity (SV) is measured by adding 8 grams of a 0.2% aqueouspolymer solution to 8.6 grams of a 2N NaCl aqueous solution, stirringthe resulting mixture for 5 minutes to dissolve the salt, adjusting thepH to 5.5 for cationic polymers and pH 8 for anionic polymers anddetermining the viscosity at 25° C. with a Brookfield viscometer (LVTmodel) with UL adapter at 60 rpm.

Examples 1-12 illustrate the preparation of a variety of polymericcompositions in an inverse microemulsion formulation.

EXAMPLE 1

Preparation of Poly(acrylamide) Inverse Microemulsion

To 2236 g of an organic solution containing 1820 g of low odor paraffinoil, 290 g of Polyoxyethylene sorbitol fatty acid ester and 126 g ofSorbitan sesquioleate is slowly added 2208.9 g of a pH=3 aqueoussolution containing 1000 g acrylamide (AMD) 60 g of acetic acid, 2 g ofisopropanol, 20.1 g of ethylenediaminetetraacetic acid tetra sodiumsalt, 1.5 g of sodium bromate, 1.4 g of sulfuric acid and 1123.9 g ofwater. The resulting monomer emulsion is sparged for 60 minutes withnitrogen. SO₂ gas is then bubbled through the emulsion at a ratemaintaining the rate of temperature increase around 2° C./min. allowinga maximum batch temperature of 65° C. Once the AMD conversion is greaterthan 99% the batch is cooled to 30° C. The result is a clear, stable PAMmicroemulsion having a SV between 3.0 and 4.0 cps.

EXAMPLE 2

Preparation of N,N-Dimethylaminomethanol (DMAM-S)

Paraformaldehyde 450 g (92%, 414 g real) is slowly added to an aqueousdimethylamine solution containing 640 g of real dimethylamine and 427 gwater while maintaining the temperature below 30° C. until the solidsdissolve. Dicyanamide 60 g and 70 g of sodium metabisulfite and 378 g ofH₂ O are added maintaining the temperature below 35° C. affordingDMAM-S.

EXAMPLE 3

Preparation of PAM-Mannich-75 Inverse Microemulsion

4425.4 g of PAM microemulsion of Example 1 is placed in a reactionvessel at ambient temperature. To this are slowly added 885.0 g of lowodor paraffin oil followed by 2025 g of DMAM-S of Example 2, the DMAM-Sbeing added over a 1.5 hour period maintaining the temperature between30°-35° C. The resulting PAM-Mannich microemulsion is stirred at thistemperature for an additional 16 hours. The resulting PAM-Mannich,7335.4 g is obtained as an opaque microemulsion.

EXAMPLE 4

Quaternization of PAM-Mannich Microemulsion of Example #3

7025.4 g of PAM-Mannich of Example 3 is placed in a stirred pressurereactor and the temperature adjusted to 25° C. To this is added 839 g ofmethyl chloride at a rate sufficient to maintain the temperature below32° C. and the reactor pressure below 30 psi. The resultingmicroemulsion is stirred at this temperature for an additional 18 hours.After this time, the pH of the emulsion is between 5 and 6 and theexcess methyl chloride removed. To the resulting microemulsion is added140 g of a 23% sodium metabisulfite solution followed by 253 g ofethoxylated nonylphenol. The resulting product is a clear, stablequaternized Mannich PAM microemulsion having an average of 75±5%cationic charge as measured by infrared spectroscopy.

EXAMPLE 5

Heat Treatment of Microemulsion of Example 4

8519.6 g of the Quaternized PAM-Mannich Microemulsion of Example 4 isplaced in a reaction vessel at ambient temperature. To this is slowlyadded with stirring 453.4 g of low odor paraffin oil and 668.9 g ofbuffer solution, which consists of 66.2 g of urea, 111.6 g of 88.5%lactic acid and 491.1 g of water. The resulting mixture is heated to 67°C. and maintained for 9 hours with agitation. The resulting product isan opaque microemulsion.

EXAMPLE 6

Preparation of PAM-Mannich-55 Inverse Microemulsion

4425.4 g of PAM microemulsion of Example 1 is placed in a reactionvessel at ambient temperature. To this are slowly added 885.0 g of lowodor paraffin oil followed by 1420.0 g of DMAM-S of Example 2, theDMAM-S being added over a 1.5 hour period maintaining the temperaturebetween 30°-35° C. The resulting PAM-Mannich microemulsion is stirred atthis temperature for an additional 16 hours. The resulting PAM-Mannich,6730.4 g is an opaque microemulsion.

EXAMPLE 7

Quaternization of PAM-Mannich Microemulsion of Example 6

6700.0 g of PAM-Mannich of Example 6 is placed in a stirred pressurereactor and the temperature adjusted to 25° C. To this is added 645.9 gof methyl chloride at a rate maintaining the temperature below 32° C.and the reactor pressure below 30 psi. The resulting microemulsion isstirred at this temperature for an additional 18 hours. After this time,the pH of the emulsion is between 5 and 6 and the excess methyl chlorideremoved. To the resulting microemulsion is added 215.9 g of ethoxylatednonylphenol. The resulting product is a clear, stable quaternizedMannich PAM microemulsion having an average of 55±5% cationic charge asmeasured by infrared spectroscopy.

EXAMPLE 8

Heat Treatment of Quaternized PAM-Mannich Microemulsion of

7197.0 g of the Quaternized PAM-Mannich Microemulsion of Example 7 isplaced in a reaction vessel at ambient temperature. To this is slowlyadded with stirring 453.4 g of low odor paraffin oil and 2032.6 g ofbuffer solution, which consists of 70.6 g of urea, 93.5 g of 88.5%lactic acid and 1868.5 g of water. The resulting mixture is heated to67° C. and maintained for 9 hours with agitation. The resulting productis an opaque microemulsion.

EXAMPLE 9

Preparation of Ammonium Acrylate/Acrylamide Copolymer Microemulsion.

An organic solution is prepared by combining a low odor paraffin oil(252.0 g), sorbitan sesquioleate (8.5 g) and polyoxyethylene sorbitolfatty acid (39.5 g) in a reactor with stirring. To this solution isadded an aqueous solution of pH=8.0 containing acrylamide (84.0 g),acrylic acid (36.0 g) neutralized with aqueous ammonium hydroxide (35.7g), tert-butyl hydroperoxide (0.048 g), ethylenediaminetetraacetic acidtetra sodium salt (0.24 g), and water (144.0 g).

The reactor is sealed and sparged with nitrogen for 30 minutes. Sulfurdioxide gas is then bubbled in to the emulsion at rate so as to maintaina temperature rise of around 2.0° C./min. The sulfur dioxide flow rateis maintained until the combined acrylic acid/acrylamide conversion isgreater than 99%.

EXAMPLE 10

Preparation of 2-Acrylamido-2-Methyl-1-Propanesulfonic Acid SodiumSalt/Acrylamide Copolymer Microemulsion.

An organic solution is prepared by combining a low odor paraffin oil(252.0 g), sorbitan sesquioleate (6.0 g) and polyoxyethylene sorbitolfatty acid (42.0 g) in a reactor with stirring. To this solution isadded an aqueous solution containing acrylamide (50.8 g),2-acrylamido-2-methyl-1-propanesulfonic acid sodium salt (69.2 g),tert-butyl hydroperoxide (0.048 g), ethylenediaminetetraacetic acidtetra sodium salt (0.24 g), and water (179.7 g).

The reactor is sealed and sparged with nitrogen for 30 minutes. Sulfurdioxide gas is then bubbled in to the emulsion at rate so as to maintaina temperature rise of around 2.0° C./min. The sulfur dioxide flow rateis maintained until the combined acrylamido-2-methyl-1-propanesulfonicacid sodium salt/acrylamide conversion is greater than 99%.

EXAMPLE 11

Preparation of Acryloyloxyethyltrimethylammonium Chloride/AcrylamideCopolymer Microemulsion.

An organic solution is prepared by combining a low odor paraffin oil(208.4 g), polyoxyethylene sorbitan monooleate (9.0 g) andpolyoxyethylene sorbitan trioleate (32.6 g) in a reactor with stirring.To this solution is added an aqueous solution, adjusted to pH=3.5 withsulfuric acid, containing acrylamide (24.0 g), acryloxyethyltrimethylammonium chloride (80.2 g), sodium bromate (0.01 g),ethylenediaminetetraacetic acid tetra sodium salt (0.21 g), and water(145.58 g).

The reactor is sealed and sparged with nitrogen for 30 minutes. Sulfurdioxide gas is then bubbled into the emulsion at rate so as to maintaina temperature rise of around 2.0° C./min. The sulfur dioxide flow rateis maintained until the combined 2-acrylamido-2-methyl-1-propanesulfonicacid sodium salt/acrylamide conversion is greater than 99%.

EXAMPLE 12

Preparation of Diallyldimethylammonium Chloride/Acrylamide CopolymerMicroemulsion.

An organic solution is prepared by combining a low odor paraffin oil(240.0 g), polyoxyethylene sorbitan monooleate (10.0 g) andpolyoxyethylene sorbitol fatty acid (50.0 g) in a reactor with stirring.To this solution is added an aqueous solution of pH=2.9 containingacrylamide (33.8 g), diallyldimethylammonium chloride (50.7 g),N-(2-hydroxyethyl) ethylenediaminetriacetic acid (0.25 g), ammoniumpersulfate (0.0032 g) and water (115.9 g).

The reactor is sealed and sparged with nitrogen for 30 minutes. Asolution of ferrous ammonium sulfate hexahydrate (0.45 wt % in water) isadded at a rate so as to maintain a reaction temperature of 30°-35° C.The ferrous ammonium sulfate hexahydrate flow rate is maintained for 20hours.

Examples 13-25 illustrate the preparation of a variety of polymericcompositions in an inverse macroemulsion formulation.

EXAMPLES 13-15

Preparation of Acrylamide/Acryloxyethyltrimethyl Ammonium ChlorideInverse Emulsion Polymers

General polymerization procedure. AMD, acryloxyethyltrimethylammoniumchloride, ammonium sulfate, glutaric acid solution,ethylenediaminetetraacetic acid tetra sodium salt solution, isopropanol,tert-butyl hydroperoxide solution, and DI water are combined and the pHadjusted to 3.5 with sulfuric acid. Sorbitan monooleate is combined withlow odor paraffin oil. The aqueous solution is slowly added to the oilsolution and the combined mixture homogenized until a viscosity of1200-1500 cps is obtained. The emulsion is sparged with nitrogen. Theemulsion is heated to 40° C. The metabisulfite (MBS) solution is addedat a rate to keep the reaction temperature between 40°-45° C. This ismaintained until the reaction conversion is at least 99%.

                  TABLE 1    ______________________________________                   Ex. 13    Ex. 14    Ex. 15    Components     20% Charge                             40% Charge                                       55% Charge    ______________________________________    Oil Phase    Oil            176.50  g     176.50                                       g   173.40                                                 g    Sorbitan monooleate                   17.90   g     17.90 g   21.00 g    Aqueous Phase    AMD (50% soln.)                   249.82  g     179.02                                       g   138.8 g    Acryloxyethyltrimethyl                   106.20  g     169.04                                       g   289.50                                                 g    ammonium chloride (80%    soln.)    Ammonium sulfate                   4.10    g     4.10  g   4.10  g    Glutaric acid (50% soln.)                   29.40   g     29.40 g   36.12 g    ethylenediaminetetra acetic                   3.92    g     4.90  g   6.00  g    acid tetra sodium salt (5%    soln.)    Isopropanol    4.20    g     3.15  g   0.75  g    tert-butyl hydroperoxide                   0.50    g     0.50  g   3.20  g    De-ionized water                   92.46   g     100.49                                       g   12.11 g    ______________________________________

EXAMPLES 16-18

Preparation of Acrylamide/Acryloxyethyltrimethyl Ammonium ChlorideInverse Emulsion Polymers

General polymerization procedure. The aqueous phase components listedbelow are combined and the pH adjusted to 3.5 with sulfuric acid. Thesorbitan monooleate is combined with low odor paraffin oil . The aqueousphase is slowly added to the oil phase and the combined mixturehomogenized until a viscosity of 1200-1500 cps is obtained. The emulsionis sparged with nitrogen and heated to 40° C. 15 mL of a 0.8 wt % sodiummetabisulfite solution in deionized (DI) H₂ O is prepared and spargedwith nitrogen. The sodium metabisulfite is added to the polymerizationmixture at a rate sufficient to maintain the temperature of the mixturebetween 40°-45° C. This is maintained until the reaction conversion isat least 99%. At the completion of the polymerization 10.0 g of a 30%wt. % solution of sodium metabisulfite in DI H₂ O is added to theemulsions containing polymer having 1 and 5% charge over 15 minutes.

                  TABLE 2    ______________________________________                   Ex. 16    Ex. 17    Ex. 18    Components     1% Charge 5% Charge 10% Charge    ______________________________________    Oil Phase    Oil            176.50  g     176.50                                       g   176.50                                                 g    Sorbitan monooleate                   17.90   g     17.90 g   17.90 g    Aqueous Phase    AMD (50% soln.)                   354.25  g     371.28                                       g   354.00                                                 g    Acryloxyethyltrimethyl                   6.10    g     33.33 g   67.13 g    ammonium chloride (80%    soln.)    Ammonium sulfate                   0.00    g     0.00  g   4.10  g    Glutaric acid (50% soln.)                   25.47   g     25.47 g   27.70 g    ethylenediaminetetra acetic                   4.25    g     4.25  g   0.00  g    acid tetra sodium salt (5%    soln.)    Pentasodium diethylenetri-                   0.00    g     0.00  g   0.58  g    amine pentaacetic acid (40%    soln.)    Isopropanol    1.83    g     2.12  g   2.31  g    NaBrO.sub.3 (2% soln.)                   0.00    g     1.00  g   2.10  g    tert-butyl hydroperoxide (2%                   1.00    g     0.00  g   0.00  g    soln.)    De-ionized water                   86.78   g     43.46 g   32.68 g    ______________________________________

EXAMPLE 19

Preparation of 2-Acryloyloxyethyltrimethylammonium Chloride/AcrylamideCopolymer (45/55 mole %) Inverse Emulsion

Polymerization Procedure

The oil phase and aqueous phase enumerated below are preparedseparately. Thereafter they are combined and homogenized to yield amonomer emulsion. The monomer emulsion is purged with nitrogen and SO₂is bubbled through the emulsion at a rate sufficient to bring theemulsion temperature up to and maintained at 40° C. This is continueduntil the polymerization is complete. The emulsion is cooled to roomtemperature and Ethoxylated alcohol--60% EO is added with stirring.

Oil Phase:

Low odor paraffin oil 177.20 g

Sorbitain monooleate 8.10 g

Ethoxylated alcohol--60% EO 12.69 g

Total Oil Phase: 197.99 g

Aqueous Phase:

Acrylamide (52.77%) 144.07 g

Acryloyloxyethyltrimethyl ammonium Chloride (80%) 315.41 g

Pentasodium diethylenetriamine pentaacetic acid (40%) 0.82 g

2-Propanol 1.12 g

Citric acid 19.68 g

DI Water 110.09 g

Sodium bromate (2.51%) 0.65 g

Aqueous Ammonia (29%) 2.16 g

Total Aqueous Phase (at pH 3.5): 594.00 g

Total Monomer Emulsion: 792.00 g

Ethoxylated alcohol--60% EO 8.00 g

Total Product Emulsion: 800.00 g

EXAMPLE 20

Preparation of Structured 2-AcryloxyethyltrimethylammoniumChloride/Acrylamide Copolymer (45/55 mole %) Inverse Emulsion

Polymerization Procedure

The oil phase and aqueous phase enumerated below are preparedseparately. Thereafter they are combined and homogenized to yield amonomer emulsion. The monomer emulsion is purged with nitrogen and SO₂is bubbled through the emulsion at a rate sufficient to bring theemulsion temperature up to and maintained at 40° C. This is continueduntil the polymerization is complete. The emulsion is cooled to roomtemperature and Malic acid and Ethoxylated alcohol--60% EO are thenadded with stirring.

Oil Phase:

Low odor paraffin oil 11939 g

N,N-bis-(2-hydroxyethyl)oleamide 524 g

Ethoxylated alcohol--60% EO 402 g

Total Oil Phase: 12865 g

Aqueous Phase:

Acrylamide (50%) 8844 g

Acryloxyethyltrimethyl ammonium Chloride (80%) 18430 g

Ammonium sulfate 250 g

Sulfuric acid (10%) 230 g

Disodium EDTA dihydrate 19 g

2-Propanol 245 g

Methylene bis(acrylamide) 0.406 g

DI Water 4021 g

t-butyl hydroperoxide (70%) 0.478 g

Total Aqueous Phase (at pH 3.5): 32039 g

Total Monomer Emulsion: 44904 g

Malic acid (50%) 2300 g

Ethoxylated alcohol--60% EO 209 g

Total Product Emulsion: 47413 g

EXAMPLE 21

Preparation of Acryloxyethyltrimethylammonium Chloride/AcrylamideCopolymer (10/90 mole %) Inverse Emulsion Containing Urea

Polymerization Procedure

The oil phase and aqueous phase enumerated below are preparedseparately. Thereafter they are combined and homogenized to yield amonomer emulsion. The monomer emulsion is purged with nitrogen and SO₂is bubbled through the emulsion at a rate sufficient to bring theemulsion temperature up to and maintained at 40° C. This is continueduntil the polymerization is complete. The emulsion is cooled to roomtemperature and Malic acid and Ethoxylated alcohol--60% EO are thenadded with stirring.

Oil Phase:

Low odor paraffin oil 175.06 g

Sorbitain monooleate 16.54 g

Ethoxylated alcohol--60% EO 4.00 g

Total Oil Phase: 195.60 g

Aqueous Phase:

Acrylamide (52.33%) 387.14 g

Acryloyloxyethyltrimethyl ammonium Chloride (80%) 76.76 g

Pentasodium diethylenetriamine pentaacetic acid (40%) 1.32 g

2-Propanol 3.43 g

DI Water 13.38 g

Urea 65.20 g

Sodium bromate (2.51%) 1.05 g

Sulfuric acid (conc.) 0.52 g

Total Aqueous Phase (at pH 3.5): 518.00 g

Total Monomer Emulsion: 713.60 g

Malic acid (50%) 68.80 g

Ethoxylated alcohol--60% EO 17.60 g

Total Product Emulsion: 832.80 g

EXAMPLE 22

Preparation of Diallyldimethylammonium Chloride Inverse Emulsion

Polymerization Procedure

The oil phase and aqueous phase are prepared separately. Thereafter theyare combined and homogenized to yield a monomer emulsion. 1.28 g of2,2'-azobis (2,4-dimethylvaleronitrile) (Vazo-52) in 10 mL of tolueneare added and the monomer emulsion is purged with nitrogen. The emulsionis heated and maintained at 60° C. for 7 hours after which time theresulting emulsion is cooled to room temperature.

Oil Phase:

Low odor paraffin oil 177.21 g

Sorbitain monooleate 8.10 g

Ethoxylated alcohol--60% EO 12.69 g

Total Oil Phase: 198.00 g

Aqueous Phase:

Diallyldimethylammonium chloride (60%) 533.33 g

Pentasodium diethylenetriamine pentaacetic acid (40%) 1.60 g

DI Water 59.07 g

Total Aqueous Phase: 594.00 g

Total Monomer Emulsion: 792.00 g

EXAMPLE 23

Preparation of Ammonium Acrylate/Acrylamide Copolymer (30/70 mole %)Inverse Emulsion

Polymerization Procedure

The oil phase and aqueous phase enumerated below are preparedseparately. Thereafter they are combined and homogenized to yield amonomer emulsion. The monomer emulsion is purged with nitrogen and SO₂is bubbled through the emulsion at a rate sufficient to bring theemulsion temperature up to and maintained at 40° C. This is continueduntil the polymerization is complete. The emulsion is cooled to roomtemperature and the sodium metabisulfite solution and Ethoxylatedalcohol--60% EO are added with stirring.

Oil Phase:

Low odor paraffin oil 162.57 g

Sorbitain monooleate 14.64 g

Ethoxylated alcohol--60% EO 5.68 g

Total Oil Phase: 182.89 g

Aqueous Phase:

Acrylamide (52.77%) 348.72 g

Acrylic acid (glacial) 79.98 g

Lactic acid (85%) 0.62 g

Pentasodium diethylenetriamine pentaacetic acid (40%) 0.53 g

t-butyl hydroperoxide (3.01%) 0.54 g

Aqueous Ammonia (29%) 66.30 g

DI Water 89.12 g

Total Aqueous Phase (at pH 7.5): 585.81 g

Total Monomer Emulsion: 768.70 g

Sodium metabisulfite (30%) 17.12 g

Ethoxylated alcohol--60% EO 14.00 g

Total Product Emulsion: 799.82 g

EXAMPLE 24

Preparation of Ammonium Acrylate/Acrylamide Copolymer (30/70 mole %)Inverse Emulsion

Polymerization Procedure

The oil and surfactants are combined. In a separate vessel theacrylamide and glacial acrylic acid are combined and cooled with an icebath to approximately 10° C. The aqueous ammonia is added slowly to pH7.0, while maintaining the monomer solution temperature below 35° C.with the use of the ice bath. The lactic acid,ethylenediaminetetraacetic acid disodium salt solution and deionizedwater are added to the monomer solution. The aqueous phase is slowlyadded to the oil phase and homogenized until a viscosity of 1200-2000cps is achieved. The emulsion is placed in a water bath at 40° C. andthe t-butyl hydroperoxide solution is added. The emulsion is purged withnitrogen for 15 minutes. 20 mL of a solution of sodium metabisulfite(MBS), 0.2% in deionized water is prepared and purged with nitrogen. TheMBS solution is added at a rate sufficient to increase the reactiontemperature to 50° C. within 30-50 minutes. The remainder of the MBSsolution is added at a rate to maintain 50° C. until the polymerizationis complete. The reaction is allowed to cool to room temperature and theaqueous ammonia, sodium metabisulfite and Ethoxylated alcohol--60% EOare added sequentially, each over a 30 minute period with stirring.

Oil Phase:

Low odor paraffin oil 145.09 g

N,N-bis-(2-hydroxyethyl)oleamide 12.60 g

Ethoxylated alcohol--60% EO 1.40 g

Total Oil Phase: 159.09 g

Aqueous Phase:

Acrylamide (50.0%) 334.18 g

Acrylic acid (glacial) 72.62 g

Lactic acid (85%) 0.56 g

ethylenediamine tetraacetic acid disodium salt (10% soln.) 7.42 g

Aqueous Ammonia (29% soln.) 67.20 g

t-butyl hydroperoxide (1.48%) 1.00 g

DI Water 57.93 g

Total Aqueous Phase (at pH 7.5): 540.91 g

Total Monomer Emulsion: 700.00 g

Aqueous Ammonia (30%) 5.60 g

Sodium metabisulfite (30%) 17.12 g

Ethoxylated alcohol--60% EO 14.00 g

Total Product Emulsion: 736.72 g

EXAMPLE 25

Preparation of 2-Acrylamido-2-Methyl-1-Propanesulfonic Acid SodiumSalt/Acrylamide Copolymer Inverse Emulsion

Polymerization Procedure

The oil phase and aqueous phase enumerated below are preparedseparately. Thereafter they are combined and homogenized to yield amonomer emulsion. The monomer emulsion is purged with nitrogen and SO₂is bubbled through the emulsion at a rate sufficient to bring theemulsion temperature up to and maintained at 40° C. This is continueduntil the polymerization is complete. The emulsion is cooled to roomtemperature and Ethoxylated alcohol--60% EO is added with stirring.

Oil Phase:

Low odor paraffin oil 175.87 g

Sorbitain monooleate 14.74 g

Ethoxylated alcohol--60% EO 5.89 g

Total Oil Phase: 196.50 g

Aqueous Phase:

Acrylamide (52.89%) 249.57 g

2-Acrylamido-2-Methyl-1-Propanesulfonic Acid Sodium Salt (50%) 264.00 g

2-Propanol 0.26 g

Pentasodium diethylenetriamine pentaacetic acid (40%) 1.32 g

t-butyl hydroperoxide (3.01%) 1.32 g

Sulfuric acid (conc.) 0.13 g

DI Water 72.90 g

Total Aqueous Phase (at pH 7.0-7.2): 589.50 g

Total Monomer Emulsion: 786.00 g

Ethoxylated alcohol--60% EO 14.00 g

Total Product Emulsion: 800.00 g

Examples 26-52 and 53-72 illustrate the preparation of a variety ofmultimodal emulsion blends arrived at by mixing a microemulsion and amacroemulsion. The data in Table 3 shows various emulsion blends madefrom a macroemulsion having a cationic functionality of 10 mole percent,based on monomer, and a polymeric microemulsion having a cationicfunctionality of 75 mole percent, based on monomer. The data forExamples 53-72 in Table 4 shows that a desired overall charge may beobtained by blending polymeric microemulsions and macroemulsions havinga variety of different charges. The data in Tables 3 and 4 shows thatone can, by using the process of the instant invention and varying theproportions of microemulsion and macroemulsion having certain percentagecationic functionality, easily obtain a stable emulsion blend having adesired charge. Moreover, by varying the standard viscosity of themicroemulsions and macroemulsions that are blended, one can easilyobtain a multimodal blend having a desired standard viscosity. Aflexible process for obtaining polymeric emulsions having a desiredoverall charge and standard viscosity is valuable because polymerflocculation performance is known to be affected by polymer charge andstandard viscosity.

EXAMPLES 26-52

Preparation of Blends

General procedure:

Polymers

The microemulsions are prepared according to Examples 1-5. The differentpolymer SVs are achieved by varying the amount of isopropanol used toprepare the PAM microemulsion of Example 1. The macroemulsions areprepared according to Example 18. The different polymer SVs are preparedby varying the amount of isopropanol added to the emulsionpolymerization. The SV of the blend is as expected from a weighedaverage of the component polymers.

Blend Preparation

The appropriate amount of the inverse macro-emulsion is weighed into abeaker. The appropriate amount of a 50 wt. % aqueous solution ofstabilizer is added to the emulsion over a period of 5 minutes withstirring. The inverse micro-emulsion is then added over 5 minutes andthe resulting blend is stirred for 30 minutes.

                                      TABLE 3    __________________________________________________________________________             Urea.sup.1                 Blend                    Macro                         Macro                              Macro                                   Urea                                       Micro                                            Micro                                                 Micro    Blend         Blend             Content                 SV.sup.2                    emulsion                         emulsion                              emulsion                                   50% emulsion                                            emulsion                                                 emulsion    Example         Charge             (wt. %)                 (cps)                    Charge.sup.3                         SV (cps)                              wt. (g)                                   soln. (g)                                       Charge                                            SV (cps)                                                 wt. (g)    __________________________________________________________________________    26   55  1.5 2.9                    10   4.0  18.2 3.1 75   2.9  81.8    27   55  1.5 2.8                    10   4.0  18.2 3.1 75   2.5  81.8    28   55  1.5 2.6                    10   4.0  18.2 3.1 75   2.3  81.8    29   55  1.5 2.7                    10   2.8  18.2 3.1 75   2.9  81.8    30   55  1.5 2.6                    10   2.8  18.2 3.1 75   2.5  81.8    31   55  1.5 2.5                    10   2.8  18.2 3.1 75   2.3  81.8    32   55  1.5 2.6                    10   2.2  18.2 3.1 75   2.9  81.8    33   55  1.5 2.4                    10   2.2  18.2 3.1 75   2.5  81.8    34   55  1.5 2.3                    10   2.2  18.2 3.1 75   2.3  81.8    35   35  2.0 3.1                    10   4.0  14.0 1.43                                       75   2.9  20.3    36   35  2.0 3.1                    10   4.0  14.0 1.43                                       75   2.5  20.3    37   35  2.0 3.0                    10   4.0  14.0 1.43                                       75   2.3  20.3    38   35  2.0 2.8                    10   2.8  14.0 1.43                                       75   2.9  20.3    39   35  2.0 2.7                    10   2.8  14.0 1.43                                       75   2.5  20.3    40   35  2.0 2.7                    10   2.8  14.0 1.43                                       75   2.3  20.3    41   35  2.0 2.4                    10   2.2  14.0 1.43                                       75   2.9  20.3    42   35  2.0 2.3                    10   2.2  14.0 1.43                                       75   2.5  20.3    43   35  2.0 2.3                    10   2.2  14.0 1.43                                       75   2.3  20.3    44   20  1.5 3.0                    10   4.0  26.6 3.1 75   2.9  73.4    45   20  1.5 2.8                    10   4.0  26.6 3.1 75   2.5  73.4    46   20  1.5 2.6                    10   4.0  26.6 3.1 75   2.3  73.4    47   20  1.5 2.8                    10   2.8  26.6 3.1 75   2.9  73.4    48   20  1.5 2.7                    10   2.8  26.6 3.1 75   2.5  73.4    49   20  1.5 2.5                    10   2.8  26.6 3.1 75   2.3  73.4    50   20  1.5 2.7                    10   2.2  26.6 3.1 75   2.9  73.4    51   20  1.5 2.4                    10   2.2  26.6 3.1 75   2.5  73.4    52   20  1.5 2.3                    10   2.2  26.6 3.1 75   2.3  73.4    __________________________________________________________________________     .sup.1 Urea added to macroemulsion (wt. % based on emulsion blend)     .sup.2 Standard Viscosity is measured centipoise (cps)     .sup.3 Cationic functionality (mole % based on monomer)

EXAMPLES 53-72

Preparation of Blends at 55% Charge

These examples demonstrate the versatility of the process of the instantinvention for blending a variety of two differently charged emulsions.It is possible to prepare blends having a desired charge from a varietyof component polymers. To compensate for the charge on the componentpolymers, one simply varies the relative amounts of macroemulsion andmicroemulsion. For the blends below the appropriate amounts of a 50%aqueous urea solution was added dropwise to the macroemulsion withstirring. The microemulsion was then added to the mixture with stirring.The different polymer SVs are achieved by varying the amount ofisopropanol use to prepare the microemulsions and macroemulsions. The SVof the blend is as expected from a weighted average of the componentpolymers.

                                      TABLE 4    __________________________________________________________________________                    Macro     Macro                                   Urea                                      Micro     Micro             Urea.sup.2                 Blend                    Emulsion                         Macro                              emulsion                                   50%                                      emulsion                                           Micro                                                emulsion    Blend         Blend             Content                 SV.sup.3                    of   emulsion                              weight                                   soln.                                      of   emulsion                                                weight    Example         Charge.sup.1             (wt. %)                 (cps)                    Example                         SV (cps)                              (g)  (g)                                      Example                                           SV (cps)                                                (g)    __________________________________________________________________________    53   55  2.5 2.7                    17   3.8  2.9  1.0                                      5    2.5  15.9    54   55  2.5 2.2                    13   2.2  4.5  1.0                                      5    2.9  13.9    55   55  2.5 2.5                    18   2.9  3.1  1.0                                      5    2.9  15.3    56   55  2.5 2.1                    13   2.2  4.5  1.0                                      5    2.0  13.9    57   55  2.5 2.4                    13   2.2  4.5  1.0                                      5    2.5  13.9    58   55  2.5 2.3                    13   2.4  4.5  1.0                                      5    2.0  13.9    59   55  2.5 2.1                    17   2.1  2.9  1.0                                      5    2.0  15.8    60   55  2.5 2.1                    13   2.2  4.5  1.0                                      5    2.0  13.9    61   55  2.5 2.8                    13   3.4  4.5  1.0                                      5    2.9  13.9    62   55  2.5 2.2                    18   3.4  3.1  1.0                                      5    2.0  15.3    63   55  2.5 2.5                    18   2.9  3.1  1.0                                      5    2.5  15.3    64   55  2.5 2.4                    18   2.2  3.1  1.0                                      5    2.9  15.3    65   55  2.5 2.8                    13   3.4  4.5  1.0                                      5    2.9  13.9    66   55  2.5 2.1                    18   2.1  3.1  1.0                                      5    2.0  15.3    67   55  2.5 2.6                    17   2.9  2.9  1.0                                      5    2.9  15.8    68   55  2.5 2.4                    18   3.4  3.1  1.0                                      5    2.0  15.3    69   55  2.5 2.5                    17   2.1  2.9  1.0                                      5    2.9  15.8    70   55  2.5 2.7                    18   3.3  3.1  1.0                                      5    2.9  15.3    71   55  2.5 2.2                    17   3.8  2.9  1.0                                      5    2.0  15.8    72   55  2.5 2.9                    17   3.8  2.9  1.0                                      5    2.9  15.8    __________________________________________________________________________     .sup.1 Cationic functionality (mole % based on monomer)     .sup.2 Urea added to macroemulsion (wt. % based on emulsion blend)     .sup.3 Standard Viscosity is measured in centipoise (cps)

Examples 73-93 demonstrate the utility of adding a stabilizer to blendsof the current invention.

EXAMPLES 73-79

Stabilization of 40% Charge Blends by Addition of Urea

Blends having an overall charge of 40% are prepared from 66.58 g of themicroemulsion of Example 5 and 35.64 g of the macroemulsion of Example18. For the samples containing urea, the appropriate amount of a 50%aqueous urea solution is added to the macroemulsion with stirring. Themicroemulsion was then added to this mixture with stirring to yield astabilized blend. The resulting blends are stored at room temperaturefor the time periods indicated. Samples of the blends are withdrawn andthe SV of the blend was measured.

                  TABLE 5    ______________________________________            Urea.sup.1 Content      Standard Viscosity    Example (wt. %)     Days @ 25° C.                                    (SV) (cps)    ______________________________________     73*    0           0           2.8                        7           1.9                        65          1.9    74      1.25        0           2.6                        65          2.8    75      2.50        0           2.4                        65          2.4    76      3.75        0           2.6                        65          2.6    77      5.0         0           3.0                        65          3.4    78      10.0        0           2.9                        42          3.1    ______________________________________     .sup.1 Urea Added to Macroemulsion (wt. % based on emulsion blend)     *Not representative of the invention for stable emulsion blends

The data in Table 5 demonstrates that when a microemulsion containingquaternized Mannich PAM, which has been heat treated with acid and aformaldehyde scavenger, is blended with a macroemulsion comprisingacrylamide/acryloxyethyltrimethyl ammonium halide copolymer (Example18), the polymer in the resulting blend does not remain stable or losesit's ability to achieve the original standard viscosity of the freshblend. But when an aldehyde scavenger (urea) is added to themacroemulsion prior to blending, the polymer in the blend remainsstable. It is known that the standard viscosity of a polymer affectsflocculation performance, as shown in Table 6, which provides sludgedewatering data for some of the emulsion blends tested in Table 5. Thedata in Table 6 demonstrates that the addition of a stabilizer to theblend allows the stabilized blend to maintain its performance efficacywhile the unstabilized blend performance deteriorates substantially withtime.

The efficiency of dewatering a typical municipal sludge is determinedfor Examples 73, 77 and 78 in Table 6 as follows: 200 gms of sludge arecarefully weighed into a beaker. Aqueous solutions of the polymers andblends are prepared by adding the polymer emulsion sample to water sothat the polymer concentration is 0.2 weight percent. Various doses ofthe polymer solution are added to the sludge samples, water is added tobring the total weight to 250 gms, the mixture is agitated at 1000 rpmfor 5 seconds and the resulting flocculated sludge is poured through aBuchner funnel containing a 60 mesh screen. The free drainage ismeasured by recording the volume of filtrate collected in 10 seconds.The resulting flocculated sludge is further dewatered by pressing thesample under identical conditions. The pressed sludge is then dried toconstant weight to determine the final sludge solids content, i.e. thecake solids.

                  TABLE 6    ______________________________________                     Age           Urea Content                     (stored at                               Dose   Filtrate                                            Cake    Example           (wt. %)   room temp.)                               (lb/ton)                                      (mL)  Solids (%)    ______________________________________     73*   0         fresh     10.4   55    --                               12.2   71    20.5                               13.2   85    20.6                               14.1   87    17.6     73*   0         6 weeks   14.1   45    --                               18.8   93    19.6                               19.8   65    19.5                               20.7   74    --                               23.5   75    --    77     5         6 weeks   9.4    53    --                               10.4   68    17.6                               11.3   48    12.9                               12.2   40    --    78     10        6 weeks   10.35  66    18.3                               10.82  74    18.7                               11.29  62    18.0                               12.24  40    --    ______________________________________     .sup.1 Urea added to macroemulsion (wt % based on blend)     *Not representative of the invention for stable emulsion blends

Table 7 shows data obtained from an accelerated aging study carried outat 50° C. This data correlates with the data of Table 5 and is thereforerepresentative of room temperature aging studies.

                  TABLE 7    ______________________________________             Urea added to.sup.1    Example  macroemulsion (wt. %)                              Days @ 50° C.                                         SV    ______________________________________     73*     0                0          2.8                              1          1.9                              4          2.1    79       0.84             0          2.6                              1          2.4                              4          2.3                              8          2.3    74       1.25             0          2.6                              1          2.6                              4          3.0                              6          2.5                              8          2.4    75       2.50             0          2.4                              1          2.4                              4          2.6                              6          2.5                              8          2.5                              10         2.4                              12         2.4    76       3.75             0          2.6                              1          2.6                              4          2.7                              6          2.7                              8          2.7    77       5.0              0          3.0                              1          3.1                              4          3.0                              6          3.1    ______________________________________     *Not representative of the invention for stable emulsion blends     .sup.1 (wt % based on emulsion blend)

EXAMPLES 80-82

Method Of Stabilizing Blends By Adding Urea To The Monomer Aqueous PhaseOf The Macroemulsion

Blends are prepared by adding the indicated amounts of the macroemulsionof Example 21 and the microemulsion of Example 5 to a beaker. The blendis mixed for a few minutes with the aid of a magnetic stirring bar. Theblends are then aged at 50° C. for the indicated time periods. Asindicated by the SV measurements, the urea in the macroemulsion issufficient to stabilize the blends, as evidenced by no loss in SV overat least one week at 50° C. In contrast, the SV of a control blend(Example 82A), prepared identically except that no urea was added to themacroemulsion, dropped to 2.0 after aging for 1 day at 50° C.

                  TABLE 8    ______________________________________           Macro-    Micro-           emulsion  emulsion        Urea.sup.1           of Example                     of Example                               Blend Content                                           Days SV    Example           21 (grams)                     5 (grams) Charge                                     (wt. %)                                           at 50°                                                (cps)    ______________________________________    80     108.35    41.35     20%   5.6   0    2.87                                           1    2.87                                           4    2.79                                           8    2.99                                           11   3.21    81     54.95     95.05     40%   2.9   0    2.82                                           1    2.82                                           4    2.77                                           8    2.81                                           11   2.84    82     19.42     80.58     55%   1.5   0    2.49                                           1    2.45                                           4    2.52                                           8    2.35                                           11   1.82    82A*   19.42     80.58     55%   0     0    2.5           (macro-                         1    2.0           emulsion of           Example 18)    ______________________________________     .sup.1 Urea added to macroemulsion (wt. % based on emulsion blend)     *Not representative of the invention for stable emulsion blend

EXAMPLES 82A-C

Effect of Order of Addition of Blend Components on Blend Stability

Stable emulsion blends were prepared at 55% overall charge by combiningthe microemulsion of Example 5 (80.6 g), the macroemulsion of Example 18(19.4 g) and optionally a 50% aqueous urea solution (4.2 g). As shown inthe Table 8A, the blends were prepared by adding either a microemulsionor macroemulsion to a vessel. To this was optionally added the aqueousurea solution over a period of 5 minutes with stirring. To this mixturethe other emulsion was added and the resulting blend was stirred for 5minutes. The control blend was unstable as evidenced by the loss in SV.Both of the stabilized blends maintained their SV after acceleratedageing. The data in Table A shows that the aldehyde scavenger may beadded to either the microemulsion or the second emulsion (heremacroemulsion) prior to blending the emulsions.

                  TABLE 8A    ______________________________________           Urea Added                    SV after    Example           (wt. % based                     Order of Addition of                                  Original                                         ageing 1    Number on blend) Components   SV (cps)                                         day at 50    ______________________________________    Control           none      1) Macroemulsion                                  2.6    2.1    Example          2) Microemulsion    82*    Example           2.0       1) Macroemulsion                                  2.6    2.7    82B              2) Urea solution                     3) Microemulsion    Example           2.0       1) Microemulsion                                  2.7    2.7    82C              2) Urea solution                     3) Macroemulsion    ______________________________________     *Not representative of the invention for stable emulsion blends

EXAMPLE 83

Stabilization of Lower Charge Microemulsion Blends By Adding Urea

Blends are prepared by adding the indicated amounts of the macroemulsionof Example 18, the microemulsion of Example 8 and a 50% urea solutionwith stirring. The overall total charge of the emulsion blend has a 24%cationic functionality, based on the monomer. The blends are then agedat 50° C. for the indicated time periods. As indicated by the SVmeasurements, the urea is sufficient to stabilize the blends containingthe lower charged quatemized Mannich PAM.

                  TABLE 9    ______________________________________          Macro-    Micro-    Urea          emulsion of                    emulsion of                              50%   Urea.sup.1                                          Days    Ex-   Example 18                    Example 8 soln. Content                                          at    SV    ample (grams)   (grams)   (grams)                                    (wt. %)                                          50° C.                                                (cps)    ______________________________________    83    22.0      22.5      5.0   5.0   0     2.9          plus 0.5 g                      1     2.9          ethoxylated                     4     2.8          alcohol -                       8     2.0          60% EO    ______________________________________     .sup.1 Urea added to blend (wt % based on emulsion blend)

EXAMPLES 84-87

Stabilization of the Macroemulsion of Example 18

The effectiveness of the aldehyde scavenger can be predicted using thefollowing test. To the macroemulsion of Example 18 is added either: a) acompound (formaldehyde or glyoxal), capable of affecting the ability ofthe (alk)acrylamide-based polymer to achieve a flocculation effectiveviscosity in water, or b) the formaldehyde or glyoxal compound in (a)plus an aldehyde scavenger (urea). The mixtures are then heated for aperiod of time, inverted and their standard viscosities are measured.The results indicate that an aldehyde scavenger is capable ofstabilizing formulations containing (alk)acrylamide-based polymer andformaldehyde or glyoxal. Since glyoxalated (alk)acrylamidemicroemulsions contain or generate glyoxal, an aldehyde scavenger wouldstabilize a blend of at least one microemulsion containing glyoxalated(alk)acrylamide polymer and at least one second emulsion containing an(alk)acrylamide-based polymer.

EXAMPLE 88

Stabilization of Blends of the Microemulsion of Example 4

A stabilized blend is prepared by mixing 50 g of the microemulsion ofExample 4, 50 g of the macroemulsion of Example 18 and 10 g of a 50%urea solution. The blend is allowed to age at room temperature for onemonth. The blend is inverted and the SV was 2.6 cps at a solution pH of7. This is essentially unchanged from the SV of the blend when preparedand illustrates that urea is effective at stablizing blends of thenon-heat-treated microemulsion of Example 4.

EXAMPLES 89-93

Stabilization of Blends by Addition of Dimedone

Blends having an overall cationic charge of 40% (mole percent, based onmonomer) were prepared from 66.58 g of the microemulsion of Example 5and 35.64 g of the macroemulsion of Example 18. For the samplescontaining dimedone, the appropriate amount of dimedone is added to themacroemulsion with stirring. The microemulsion was then added to thismixture with stirring to yield a stabilized blend. The resulting blendsare stored at 50° C. for the indicated time period. Samples of theblends are withdrawn and the SV of the blend is measured. The resultsindicated that dimedone (5,5-dimethyl-1,3-cyclohexyldione) is alsoeffective at stabilizing the emulsion blends.

                  TABLE 11    ______________________________________    Example  Dimedone.sup.1 (wt. %)                             Days @ 50° C.                                        SV    ______________________________________     89*     0               0          2.8                             1          1.9                             4          1.9    90       1.25            0          2.6                             1          2.6                             4          2.6                             6          3.0                             8          2.5                             14         2.4    91       2.50            0          2.4                             1          2.4                             4          2.4                             6          2.6                             8          2.5                             10         2.5                             12         2.4                             16         2.4    92       3.75            0          2.6                             1          2.7                             4          2.5                             6          2.7                             8          2.7                             16         2.3    93       5.0             0          3.0                             1          3.1                             4          3.0                             6          3.1    ______________________________________     .sup.1 Dimedone added to macroemulsion (wt % based on emulsion blend)     *Not representative of the invention for stable emulsion blends

MULTIMODAL EMULSION BLEND VISCOSITY DATA

Examples 94-111 demonstrate that the instant process for preparingmultimodal emulsions can conveniently provide for emulsion blends thatdisplay bulk viscosities that are lower than a weighted average of thetwo parent emulsions.

EXAMPLE 94

Blends of the microemulsion of Example 5 containing a quaternary Mannichmicroemulsion and the low charge cationic macroemulsion of Example 18were prepared. The blends have a lower viscosity than either themacroemulsion or microemulsion.

                  TABLE 12    ______________________________________    wt. %    microemulsion  Bulk Viscosity    in blend       (cps).sup.2    ______________________________________      0.sup.1*     1740    10             1040    20             835    30             678    40             581    50             511    60             496    70             564    80             755    90             1090     100*          2100    ______________________________________     .sup.1 (100 wt% macroemulsion)     .sup.2 measured using a Brookfield Viscometer LVT model #2 spindle, 12rpm     *Not representative of the invention of preparing multimodal emulsion     blends

EXAMPLES 95-111

Blends Viscosity vs. Composition

A variety of blends of different inverse microemulsions and inversemacroemulsions are prepared. The polymer combinations includecationic/cationic, cationic/anionic and anionic/anionic polymer blends.Table 13 shows examples of these types of blends and the viscosity ofthe blends measured in centipoise at room temperature using a Brookfieldviscometer using a #2 spindle and 12 rpm. The resulting blends aremultimodal and advantageous in that they display a viscosity which islower than that of a weighted average of the two parent inverseemulsions used to prepare the multimodal emulsion blends.

                                      TABLE 13    __________________________________________________________________________                    Weight Percent Microemulsion in the Blend    Blend Type      (viscosity - cps)         Micro                      0*         emulsion              Macro                 (100%         of   emulsion              macro-    Example         Example              of Example                    100%*                        75% 50% 25% emulsion)    __________________________________________________________________________     95  9    21    28  55  177 433  960     96  9    25    28  53  190 461 1380     97  9    22    28  65  259 615 4530     98  9    23    28  55  242 621 1650     99  9    24    28  53  197 504 1220    100  10   23    25  68  245 574 1650    101  10   21    25  43   98 292  960    102  10   22    25  70  329 --  .sup. 4530.sup.1    103  11   21    15  45  115 329  960    104  11   22    15  48  185 486 4530    105  12   21    15  60  234 539  960    106  5    25    2300                        626 417 611 1380    107  5    22    2300                        386 361 585 4530    108  5    19    2300                        822 628 698 1100    109  5    23    2300                        768 523 748 1650    110  5    20    2300                        346 372 561 1070    111  5    24    2300                        1010                            625 748 1220    __________________________________________________________________________     .sup.1 #3 spindle used     *Not representative of the invention or preparing multimodal emulsion     blends

EXAMPLE 111A

Low Viscosity Emulsion Blend of Two Microemulsions

The microemulsion of Example 1 having a volume average droplet diameterof 650 Å, (as measured by transmission electron microscopy) and themicroemulsion of Example 5 having a volume average droplet diameter ofabout 1000 Å are blended together as indicated below. The resultingblend is a multimodal emulsion blend which has a viscosity which is lessthan that predicted by a weighted average of the starting emulsionviscosities.

                  TABLE 14    ______________________________________    Blend    Composition       Blend    (wt. %)           Viscosity    Ex. 1          Ex. 5  .sup.1(cps)    ______________________________________    100            0      28    75             25     45    50             50     78    25             75     249    0              100    1260    ______________________________________     .sup.1 Brookfield Viscometer, LVT model with UL adapter 12rpm

Examples 112-118 demonstrate the performance utility of various stablemultimodal emulsion blends.

EXAMPLES 112-188

The efficiency of dewatering a typical municipal sludge is determined inExamples 112-118 as follows: 200 gms of sludge are carefully weighedinto a beaker. Aqueous solutions of the polymers and blends are preparedby adding the polymer emulsion sample to water so that the polymerconcentration is 0.2 weight percent. Various doses of the polymersolution are added to the sludge samples, water is added to bring thetotal weight to 250 gms, the mixture is agitated at 1000 rpm for 5seconds and the resulting flocculated sludge is poured through a Buchnerfunnel containing a 60 mesh screen. The free drainage is measured byrecording the volume of filtrate collected in 10 seconds. The resultingflocculated sludge is further dewatered by pressing the sample underidentical conditions. The pressed sludge is then dried to constantweight to determine the final sludge solids content, i.e. the cakesolids.

As demonstrated by the data in Examples 112-118, the stable multimodalemulsion blends of Examples 114, 115, 116 and 117 exhibited improvedflocculation performance compared to single macroemulsions containingpolymers of similar charge.

EXAMPLE 112

Performance of 55% Charge Blends on Typical Municipal Sludge #2

                  TABLE 15    ______________________________________              Control of          Filtrate                                         Cake    Blend of Example              Example   Dose(mL)  (mL)   Solids (%)    ______________________________________    30                  10        130    27.3                        12        148    29.7                        14        158    28.7                        16        165    30.1              15*       10        140    28.4                        12        152    30.8                        14        148    28.6                        16        150    27.1    ______________________________________     *Not representative of the invention for preparing multimodal emulsion     blends or the invention for stable emulsion blends

EXAMPLE 113

Performance of 55% Charge Blends on Typical Municipal Sludge #3

                  TABLE 16    ______________________________________              Control of                        Dose      Filtrate                                         Cake    Blend Example              Example   (mL)      (mL)   Solids (%)    ______________________________________    30                  16        103    19.8                        18        135    20.3                        19        135    20.4                        20        147    19.0                        22        148    19.2    27                  16        128    19.1                        18        143    18.9                        20        137    19.6    33                  18         74    19.7                        22        126    20.4                        24        137    21.1              15*       16         68    19.6                        18        141    19.2                        20        152    18.6                        22        151    18.4    ______________________________________     *Not representative of the invention for preparing multimodal emulsion     blends or the invention for stable emulsion blends

EXAMPLE 114

Performance of 20% Charge Blends on Typical Paper Sludge

Tested with an agitation 500 rpm for 5 seconds. Filtrate quality isassessed by measuring clarity, in NTU with a Hach turbidimeter.

                  TABLE 17    ______________________________________               Control of                        Dose      Filtrate                                        Turbidity    Blend Example               Example  (mL)      (mL)  (NTU)    ______________________________________    44                  9         106   141                        12        126   38                        15        122   76                        18        124   50    45                  9         114   180                        12        140   44                        15        142   33                        18        148   44    46                  9         118   191                        12        138   40                        15        148   30                        18        138   43    49                  9         100   294                        12        134   54                        15        148   35                        18        146   44               13*      9          50   >500                        12        102   164                        15        138   83                        18        144   47    ______________________________________     *Not representative of the invention for preparing multimodal emulsion     blends or the invention for stable emulsion blends

EXAMPLE 115

Performance of 55% Charge Blends on Municipal Sludge #4

                  TABLE 18    ______________________________________                Control of                         Dose     Filtrate                                        Cake    Blend of Example                Example  (mL)     (mL)  Solids (%)    ______________________________________    30                   12       92    24                         14       136   22                         16       150   22                         18       148   23                15*      12       72    24                         14       104   24                         16       125   27                         18       148   23    ______________________________________     *Not representative of the invention for preparing multimodal emulsion     blends or the invention for stable emulsion blends

EXAMPLE 116

Performance of 55% Charge Blends on Municipal Sludge #5

                  TABLE 19    ______________________________________                Control of                         Dose     Filtrate                                        Cake    Blend of Example                Example  (mL)     (mL)  Solids (%)    ______________________________________    30                   18       84    17                         20       116   16                         22       127   16                         24       110   17                15*      18       98    16                         20       108   17                         22       104   16                         24       106   17    ______________________________________     *Not representative of the invention for preparing multimodal emulsion     blends or the invention for stable emulsion blends

EXAMPLE 117

Performance of 20% Charge Blends on Municipal Sludge #6

                  TABLE 20    ______________________________________                Control of                         Dose     Filtrate                                        Turbidity    Blend of Example                Example  (mL)     (mL)  (NTU)    ______________________________________    44                   5        56    765                         6        74    432                         7        76    284                         8        88    183                         9        88    110                         10       90    111                         12       88    98    45                   5        50    >1000                         6        58    678                         7        56    440                         8        66    309                         9        70    256                         10       84    159                         12       106   98                         14       94    112                13*      5        54    >1000                         6        66    581                         7        72    363                         8        88    210                         9        100   123                         10       94    83                         12       100   43    ______________________________________     *Not representative of the invention for preparing multimodal emulsion     blends or the invention for stable emulsion blends

EXAMPLE 118

Preparation And Performance Of Blends

Blends in Example 110 are prepared by mixing the emulsion of Examples 5and 20, then stabilized by urea at a level of 1.5-2.0%, and tested usingtypical sludge #7. Example 110 and 30 blends show effective performancecomparable to the emulsions used to prepare the emulsion blend 110.

                  TABLE 21    ______________________________________                Control of         Filtrate                                          Turbidity    Blend Example                Example   Dose(mL) (mL)   (NTU)    ______________________________________    110                   8        88     --    Micro/Macro = 1/1 g/g 10       125    22                          12       129    22                          14       120    --    110                   8        87     --    Micro/Macro = 1/3 g/g 10       125    20                          12       135    22                          13       124    22                          14       133    --    30                    8        77     --                          10       125    22                          12       131    23                          14       129    24                5*        8        82     --                          10       124    22                          12       136    22                          14       121    21                          16       120    21                          18       105    20                20*       8        77     --                          10       121    21                          12       132    23                          14       117    --    ______________________________________     *Not representative of the invention for preparing multimodal emulsion     blends or the invention for stable emulsion blends

The preceding examples can be repeated with similar results bysubstituting the generically or specifically described reactions and/oroperating conditions of this invention for those used in the precedingexamples.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and withoutdeparting from the spirit or scope of the invention, can make variousmodifications of the invention to adapt it to various applications.

We claim:
 1. A method of flocculating suspended solids in an aqueousdispersion which comprises adding to said aqueous dispersion aflocculating amount of an emulsion blend of:(a) at least one inversemicroemulsion comprising a continuous phase and a water-swellable orwater-soluble addition polymer-containing discontinuous phase in theform of droplets having a volume average droplet diameter; wherein saidmicroemulsion comprises surfactant in a concentration sufficient to forman inverse microemulsion; and (b) at least one second emulsioncomprising a continuous phase and a water-swellable or water-solubleaddition polymer-containing discontinuous phase in the form of dropletshaving a volume average diameter which is greater than the volumeaverage diameter of the droplets in said microemulsion, wherein saidpolymer in said microemulsion is different than said polymer in saidsecond emulsion.
 2. A method according to claim 1 wherein the volumeaverage droplet diameter of the droplets in said second emulsion is atleast about 300 Å greater than the volume average droplet diameter ofthe droplets in said microemulsion.
 3. A method according to claim 1wherein said second emulsion is a macroemulsion.
 4. A method accordingto claim 1 wherein said polymer in said microemulsion is cationic.
 5. Amethod according to claim 1 wherein said polymer in said microemulsionis anionic.
 6. A method according to claim 1 wherein said polymer insaid microemulsion is:(a) a cationic polymer containing monomeric unitsselected from: quaternary dialkyl aminomethyl (alk)acrylamide; dialkylaminomethyl (alk)acrylamide; quaternary dialkylaminoalkyl(meth)acrylates; quaternary dialkylaminoalkyl (meth)acrylamides;dialkylaminoalkyl (meth)acrylates; dialkylaminoalkyl (meth)acrylamides;diallyldialkylammonium halides and copolymers thereof with(alk)acrylamide; (b) an anionic polymer selected from: a copolymer of(alk)acrylamide with one or more anionic monomers selected from acrylicacid, methacrylic acid, their ammonium or alkali metal salts; vinylsulfonic acid and 2-acrylamido-alkylsulfonic acid and their salts; andhomopolymers of (meth)acrylic acid, acrylic acid, vinyl sulfonic acid,2-acrylamido-alkylsulfonic acid or their salts; or (c) a nonionicpolymer containing monomeric units selected from: acrylamide andmethacrylamide.
 7. A method according to claim 1 wherein the ratio ofmicroemulsion to second emulsion ranges from about 95:5 partsmicroemulsion to second emulsion to about 5:95 parts microemulsion tosecond emulsion.
 8. A method according to claim 1 wherein:said polymerin said microemulsion is a water-soluble polymer-based polymer havingfunctional groups which are capable of continually crosslinking atambient conditions.
 9. A method according to claim 1 wherein the volumeaverage droplet diameter of the droplets in said second emulsion is atleast about 1000 Å greater than the volume average droplet diameter ofthe droplets in said microemulsion.
 10. A method according to claim 1wherein the second emulsion is a macroemulsion.
 11. A method accordingto claim 1 wherein the water-soluble polymer-based polymer in saidmicroemulsion is a vinylic addition polymer containing monomeric unitsselected from acrylamide; glyoxalated (alk)acrylamide; anhydroxyalkyl(alk)acrylate, an N,N-dialkylaminoalkyl(alk)acrylate and anallyl amine.
 12. A method of flocculating suspended solids in an aqueousdispersion which comprises:adding to said aqueous dispersion aflocculating amount of an emulsion blend of:(a) at least one inversemicroemulsion, said microemulsion comprising a continuous phase and awater-soluble addition polymer-containing discontinuous phase in theform of droplets having a volume average droplet diameter; said polymerin said microemulsion being a dialkyl aminomethyl (alk)acrylamidepolymer or quaternized product thereof; and said microemulsioncomprising surfactant in a concentration sufficient to form an inversemicroemulsion; and (b) at least one second emulsion comprising acontinuous phase and a water-swellable or water-soluble additionpolymer-containing discontinuous phase in the form of droplets having avolume average diameter which is greater than the volume averagediameter of the droplets in the microemulsion, wherein said polymer insaid microemulsion is different than said polymer in said secondemulsion.
 13. A method according to claim 12 wherein the volume averagedroplet diameter of the droplets in said second emulsion is at leastabout 300 Å greater than the volume average droplet diameter of thedroplets in said microemulsion.
 14. A method according to claim 12wherein the second emulsion is a macroemulsion.
 15. A method accordingto claim 12 wherein the polymer in said second emulsion is:(a) ananionic polymer selected from:a copolymer of (alk)acrylamide with one ormore anionic monomers selected from acrylic acid, methacrylic acid, andtheir alkali metal or ammonium salts; vinyl sulfonic acidacrylamido-2-methyl propanesulfonic acid and their salts; andhomopolymers of (meth)acrylic acid, acrylic acid, vinyl sulfonic acid oracrylamido-2-methyl propanesulfonic acid; or (b) a nonionic polymercontaining monomeric units selected from:acrylamide and methacrylamide.16. A method according to claim 12 wherein the polymer in said secondemulsion is a cationic polymer containing monomeric units selected fromquaternary dialkyl aminomethyl (alk)acrylamides, dialkyl aminomethyl(alk)acrylamides; quaternary dialkylaminoalkyl (meth)acrylates;quaternary dialkylaminoalkyl (meth)acrylamides; dialkylaminoalkyl(meth)acrylates; dialkylaminoalkyl (meth)acrylamides;diallyldialkylammonium halides and copolymers thereof with(alk)acrylamide.
 17. A method according to claim 12 wherein the volumeaverage droplet diameter of the droplets in said second emulsion is atleast about 1000 Å greater than the volume average droplet diameter ofthe droplets in said microemulsion.
 18. A method according to claim 12wherein the polymer in said microemulsion is a dialkyl aminomethyl(alk)acrylamide polymer or quaternized product thereof containing fromabout 20 to about 100 mole percent cationic functionality, and thecationic polymer in said second emulsion contains from about 1 to about60 mole percent cationic functionality.
 19. A method of flocculatingsuspended solids in an aqueous dispersion which comprises:adding to saidaqueous dispersion a flocculating amount of an emulsion blend of:(a) atleast one inverse microemulsion, said microemulsion comprising acontinuous phase and a water-soluble polymer-containing discontinuousphase in the form of droplets having a volume average droplet diameter;said polymer in said microemulsion being a dialkyl aminomethyl(alk)acrylamide polymer or quaternized product thereof and saidmicroemulsion comprising surfactant in a concentration sufficient toform an inverse microemulsion; and (b) at least one macroemulsioncomprising a continuous phase and a water-swellable or water-solublepolymer-containing discontinuous phase in the form of droplets having avolume average diameter which is at least about 300 Å greater than thevolume average diameter of the droplets in the microemulsion; saidpolymer in said macroemulsion being a copolymer of acrylamide and(meth)acryloyloxyethyltrimethylammonium salt.
 20. A method according toclaim 19 wherein said dialkyl aminomethyl (alk)acrylamide polymer orquaternized product thereof contains from about 20 to about 100 molepercent cationic functionality, and said copolymer of (alk)acrylamideand (meth)acryloyloxyethyltrimethylammonium salt contains from about 1to about 60 mole percent cationic functionality.
 21. A method accordingto claim 19 wherein said dialkyl aminomethyl (alk)acrylamide polymer orquaternized product thereof contains from about 60 to about 90 molepercent cationic functionality, and said copolymer of (alk)acrylamideand methacryloyloxyethyltrimethylammonium salt contains from about 1 toabout 20 mole percent cationic functionality.
 22. A method offlocculating suspended solids in an aqueous dispersion whichcomprises:(a) converting a composition, made from a blend of at leasttwo emulsions, into a dilute aqueous solution, wherein at least one ofsaid two emulsions is an inverse microemulsion comprising a continuousphase and a water-swellable or water-soluble addition polymer-containingdiscontinuous phase in the form of droplets having a volume averagedroplet diameter and wherein said microemulsion comprises surfactant ina concentration sufficient to form an inverse microemulsion and thesecond of said two emulsions in said blend comprises a continuous phaseand a water-swellable or water-soluble addition polymer-containingdiscontinuous phase in the form of droplets having a volume averagediameter which is greater than the volume average diameter of thedroplets in said microemulsion; and (b) adding to said aqueousdispersion a flocculating amount of said aqueous solution, wherein saidpolymer in said microemulsion is different than said polymer in saidsecond emulsion.
 23. A method according to claim 22 wherein saidcomposition is converted to said aqueous solution by inverting saidcomposition.
 24. A method according to claim 22 wherein said compositionis converted to said aqueous solution by recovering one or morewater-swellable or water-soluble polymers from said composition andadding the recovered polymer to water.